Justin
A. Fye
ARCH
45240: The Skyscraper
Professor
Robison
27-November-2012
terror
(n.) - the
purposeful and deliberate targeting of noncombatants with acts of violence[1]
American
Cities and Skyscrapers: Perseverance after 9/11
“A great people have been moved to defend a
great nation. Terrorist attacks can shake the foundations of our biggest
buildings, but they cannot touch the foundation of America. These acts
shattered steel, but they cannot dent the steel of American resolve.”[2]
This message was delivered by President George W. Bush on the evening of
September 11th, 2001, speaking of the devastating terrorist attacks
on America, the largest on American soil since Pearl Harbor in 1941. On this
brutal day in America’s history, citizens across the country stood in shock and
disbelief after the World Trade Center Towers collapsed, the Pentagon was attacked,
and an attempted attack on the White House was thwarted as a result of extreme
bravery and the ultimate sacrifice. Rightfully so, these attacks raised many
questions about the security and future of America in nearly all facets of life.
Some of the greatest questions about America’s future after September 11th
focused on how the attacks would affect urban centers and their life form, the
skyscraper. How would America respond to 13.4 million square feet of class A
office property in New York City being destroyed? And another 14.4 million
square feet being damaged?[3]
Although many expected a great shift in thought about utilizing these tall
structures, and the cities which stabilize them, as workplace, residence, and economic
catalyst, the great American art form would survive and persevere, just as the
American people would.
In the months following 9/11, there
was a rapid knee jerk reaction towards the future of the skyscraper by many
critics, both within and outside of the architecture field. As the New York
City office market witnessed a downturn in revenue and increasing vacancies, a
1.1% increase from September to November 2001[4],
many experts offered their opinions on the future of skyscrapers. Two notable
urban critics, Kunstler and Salingaros, stated, “The age of skyscrapers is at
an end. It must now be considered an experimental building typology that has
failed.”[5] This
opinion is narrow minded, though. Although the events of September 11th,
2001 exposed many issues with skyscrapers and cities, such as security and mass
evacuation incapability, as well as a limited scope on possible structural
issues considered during the design phase, it is unfair to label skyscrapers as
failures. Despite the possible consequences of placing such a great number of
inhabitants into a single building which must be evacuated in an emergency
circumstance, as was seen on 9/11, the skyscraper form will never go extinct
due to the immense amount of economic possibility such a large structure can
provide, in contrast to the small percentage of issues such buildings typically
cause. When done properly, the economics of skyscrapers are hardly failures,
and in the capitalistic society of America, economics undoubtedly rule. Sharon
Zukin, a Manhattan cityscape critic, expressed her desire for New York City to
learn from the World Trade Center Towers, stating, “We need to rebuild a lower
scale downtown where life hums and throbs on every block.”[6] Coinciding
with Ms. Zukin’s opinion, Edwin Mills, an economist who teaches at Northwestern
University, stated, “Increasing dangers of terrorist attacks…will lead to lower
CBD land values and hence to lower office building heights.”[7]
Although the trend which was expected by Mr. Mills would have leaned toward the
possibility of the lower scale downtown Ms. Zukin was speaking of, it was
hardly the first time such a desire was expressed by residents of the New York
City metropolitan area. “Debates about the significance and efficiency of
skyscrapers have been raging since the [skyscraper] was invented more than a
century ago,”[8]
however, events such as the imposing of the setback laws have dealt with the
issues being proposed here, and provide a precedent for how to handle these
issues. A continuation of the debate on a cap of building heights in the New
York area attempts to set back growth, knowledge and technology nearly 100
years.
Cesar
Pelli, the architect of Petronas Towers, had an opposing opinion, stating,
“Once the current threat is gone and we all feel comfortable again, the desire
to build tall buildings will reassert itself...I believe that the skyscraper is
part of the nature of human beings.”[9] The
reality of the American capitalistic economy is such that so long as there is
substantial money to be made, developers will continue to build skyscrapers,
and tenants will continue to inhabit them for their office needs, despite the
possible risks. Skyscrapers are, then, in the nature of human beings, as Pelli
suggests, because of their great economic possibilities. This idea was further
supported when a real estate firm which was tasked with monitoring the
relocation patterns of World trade Center tenants after 9/11 noted that two
years after the terrorist attacks, “52% of the total affected space was
reoccupied, backfilled, and leased in downtown [New York City].”[10]
This statistic proved not only that downtown tall office buildings would
recuperate, but shows just how quickly it occurred as well.
While skyscrapers in New York City
experienced a fairly quick recuperation in response the 9/11 attacks, a greater
question arose as to how cities and their residents across America would
respond in the long term. Was it possible such an attack could create urban
sprawl causing the dynamic of cities, and thus their most visible form, to
adapt to a new way of life? In order to answer this question, cities must be
investigated historically. Although economists have always stressed the role of
cities as “centers for commerce or industry,” a longer view of the history of
cities shows that their historic purpose may have actually been primarily
protection.[11]
Edward L. Glaeser, author of Cities and
Warfare: The Impact of Terrorism on Urban Form, notes that broadly speaking
there are three main ways in which terrorism has affected urbanization.[12]
Historically, cities have been looked at as safe harbors, and are likely the
main reason for their development overall. Recently, however, acts of danger,
such as terrorism, have driven up the cost of transportation and have created a
target effect, which could cause people to want to disperse. The problem is
that, currently, “cities are in the peculiar position of serving as [both]
incubator…and target of terror.” It is of human nature to feel comfortable in
groups, such as are present in the masses within cities. Concentrations of
people have an advantage in defending themselves, thus making cities more
appealing in times of violence. Issues arise, however, in that “the essence of
terrorist technologies is that they enable small groups to inflict harm on much
larger populations.”[13]
The advantage which terrorism fundamentally relies upon, then, negates the safe
harbor effect which was historically employed by cities to ensure civilian
safety. Terrorism ultimately relies upon urban density, or the ability to
destroy a large amount in a small amount of time. This sentiment has become
even more evident in the modern era with the advent of macro terrorism, which
aims to kill large numbers of people, not only in a consolidated location, but
in a single blow. September 11th proved this, as the attack
“targeted the single highest density area in the United States,” New York City,
and did so utilizing a singular means of attack.[14] The
events of 9/11 were among the most significant in recent history because they
“catalyzed a trend toward urban based terror that had been building for a
decade or more.”[15]
Despite these types of attacks being present for some time prior to the attacks
on American soil, their success in the United States seems to have solidified
the method as the most desirable. “Taking a recent eight year period, cities
accounted for 64% of terror attacks, 61% of total fatalities, 94% of injuries,
and 86% of physical damage.”[16] Unfortunately,
this trend shows no sign of changing at any point in the near future, as research
shows “more than 250 cities across the globe have experienced some act of
terror.”[17]
So
does urban targeted macro terrorism spell the end for the city, and thus the
skyscraper, as we know it? As Witold Rybcznyski, a professor of architecture
and urbanism at the University of Pennsylvania, points out, not at all. “Tall
buildings have a huge effect on the American city…American cities do not have
plazas and boulevards and great palaces, but what we have is skyscrapers. It is
very much the character of our city. So when people say we should stop building
them, we need to think very hard about that because it means we stop building
cities the way we have been building them for more than 100 years.”[18]
American cities, from New York to Chicago to Los Angeles, and more, have been
far too successful to consider a drastic shift away from the urban city centers
that have come to shape the country, at least as a result of one significant
terrorist attack. Continued future attacks could lead to greater reasoning for
such a change. Historically, however, not even large numbers of attacks could
significantly alter urban forms. In a recent review of the impact of warfare
and terrorism on urban form, Glaeser and Shapiro used Jerusalem and London, two
cities which have experienced vast amounts of terrorist attacks, as examples to
investigate growth patterns of cities under the threat of terrorism.
Interestingly, little impact on the growth of either city was found, proving that
most people feel safe enough within cities; as if they believe terrorism will
only happen to someone else.[19]
This feeling is synonymous with the American psyche which tends to rely upon
invincibility. These results are unlikely to change when applied to the future
construction of skyscrapers, and thus point to a continued proliferation of
tall structures within American cities. The advantages which cities rely upon
for their successfulness, “physical beauty, a strong tourist economy, and
historical significance,” outweigh the relative dangers of terrorism, as safety
concerns continue to be covered up by the “conflict between commercial and
aesthetic values.”[20]
Although in the short term it appeared as though there would be significant
residual effects as a result of 9/11, as 41% of American cities reported that
their economies had weakened within the first month after the event[21],
the hardest hit areas were generally the large metropolises such as New York
City, Los Angeles, Chicago, Boston, Seattle, and Atlanta, and those cities
would recuperate as a result of the advantages described above.
Some
scholars have conflicting ideas about the future of cities and skyscrapers,
however. For cities, “the most alarming economic news lies in skyrocketing
costs for buildings and public events. In the United States, banks and
insurance companies have either refused to underwrite large scale projects or
charged enormous premiums to do so. More than $15.5 billion in real estate
projects were suspended, or cancelled, because developers could not obtain
insurance.”[22]
Because of this, some scholars say investors are shying away from building
skyscrapers. Kunstler and Salingaros again portrayed their lack of faith in
American cities and skyscrapers, stating, “Unfortunately, momentum appears to
favor a shift away from traditional cities and toward sprawl suburbs.”[23]
Although this might be true for more recently developed metropolitan areas
which do not already have a solid base of skyscrapers, such as those present in
Arizona, new skyscrapers continue to be built in the more traditional cities
such as New York and Chicago, both which have seen new significant skyscrapers
in the forms of Freedom Tower and Trump International Hotel and Tower
respectively.
Also,
the attacks of September 11th undeniably left Americans with a
greater sense of insecurity than any other time in recent history. A survey
conducted by the Economist uncovered that “more than 60% of Americans
believe[d] the nation [would] suffer further attacks of terrorism,” and another
survey conducted by the New York Times in partnership with CBS News found that,
“26% of New Yorkers felt uneasy about going into a skyscraper.”[24] Given
the tragic events that took place, however, these feelings had to have been
expected. It is logical to think that after some time has passed, as Cesar
Pelli suggests, the uneasy feelings should subside, and a comfort level will
again be reached.
The
most reasonable, and thus problematic, of the scholarly opinions which conflict
with the continued success of the city and skyscraper is that of Cullen and
Levitt, who attempted to link crime and city populations with the possible
effects of terrorism. Using data from more than one hundred cities over two
decades, they found that rising crime depressed city populations. Based on
their findings they stated, “When life and property are jeopardized, people
flee inner cities and seek safety elsewhere.”[25]
They also found the most likely of those to leave cities in the wake of crime
to be the middle class, well educated residents; the exact people who truly
keep the city afloat. If the effects of terrorism and crime can truly be linked
and compared, as it seems as though they should, it is seemingly possible
future continued terrorist attacks could jeopardize the well being of city
dwellers and workers, and thus the well being of the city itself, and all of
its components, including skyscrapers.
In
actuality, post 9/11 high rise office buildings continue to exhibit the same
fundamentals that made them successful before 9/11, specifically, their
proximity to clients, banks, governmental institutions, services, restaurants,
and more.[26]
Even directly after the attacks, preliminary findings indicated that tall
office buildings had not suffered as a result of 9/11 in comparison to the
general office market. Well known, famous buildings, however, did suffer
significant economic consequences. Based on an extensive study completed by
Costar Data, it was determined that when “the most famous property in New York
City and Chicago was separated from the tall and trophy group [of skyscrapers],
a significant relative increase was observed in the vacancy rates and sublease
activity within these famous buildings, relative to the overall market.”[27]
One of the leading indicators of building trends, vacancy rates, showed that
the tallest buildings, those fifty or more stories, in particular recorded a
sharp change in vacancy rates after 9/11.[28] This
trend is further depicted in Figure 1 of the attached appendix. This data,
then, suggests that a greater effect on the most famous skyscraper property
could be as a result of such buildings being more of a distinct target for
terrorists to attack. This is entirely understandable when one truly
investigates the targets attacked on September 11th.
The attacks were “directed not just at
physical targets, but at representations of power.”[29] The
World Trade Center towers were symbols of America’s economic world, the
Pentagon its military might, and The White House its political power. The
selection of these targets was, of course, very deliberate and thus should
provide some insight into the types of buildings which could become potential
targets in the future for terrorists. It is justifiable, then, to hypothesize
that the most famous skyscrapers in America, both symbolic for popularity and
with the capacity to hold large numbers of civilians, are the greatest
potential future targets. It is also reasonable to think that the tallest
buildings which receive the most visibility could become the greatest future
targets. One significant example of the effect of 9/11 on tall, famous
buildings was the Trump International Hotel and Tower in Chicago. Prior to the
September 11th events, Donald Trump had decided to build the world’s
tallest building, 130-150 stories. Instead, an 86 story building was approved
in July 2002, making it Chicago’s fourth tallest building. When asked about the
downgrade in size, Trump stated, “the age of great skyscrapers will never
cease, but as for the race to build the world’s tallest building, there is
going to be a little bit of a pause.”[30]
This thought process can be directly related to the attacks of 9/11 and the
idea that a super tall building of high fame could become an easy target for
future terrorist attacks on the United States. One thing is for certain; if
Donald Trump, one of the world’s most ambitious business owners and real estate
moguls, had backed off of building super tall structures, other developers were
taking the same precautions. Will the susceptibility of famous buildings to
terrorist attacks in the future lead tenants in search of lower height
buildings though? It is unlikely. As Norman Miller and Torto Wheaton point out,
famous buildings are famous because they are well known. This makes them
extremely desirable to tenants and investors because of their vast amount of
visibility. Also, in contrast to what many scholars had predicted, there was
not a flight from tall buildings due to psychological reasons and fear of new
attacks[31].
It is evident, then, that the self advertising a building can provide for ones
company can sometimes be enough, economically, to outweigh the building owner’s
concerns about the susceptibility to future problems.
Another
common belief following the September 11th attacks was that “the
susceptibility of famous buildings and very tall buildings to terrorist attacks
in the future might lead tenants in search of office space to move to low
height and low profile buildings instead of the most prestigious and conspicuous
buildings, which were favored locations before 9/11.” In the years following
the attacks, however, no such dispersal from tall office property has occurred.
In fact, developers and architects have continued to push the envelope of
construction higher than ever before. In the three year period following the
attacks, September 2001-2004, eight new super tall buildings were approved
across the world, three of which were in the United States[32].
As is shown in Figure 2 of the appendix, the Waterview Tower in Chicago, Trump
International Hotel and Tower in Chicago and Freedom Tower in New York City
continued the skyscraper trend in the United States, while buildings like the
Burj Dubai reached for the record of the world’s tallest building. Such
evidence proves, once again, that Cesar Pelli was correct in stating the desire
to build tall would reassert itself after the initial trepidations had been
removed from Americans. In reality, this likely occurred much faster than most
expected.
Considering
the knowledge set forth, some final questions become, where do the future of cities
and skyscrapers lie? What factors will determine their successes? And what
future dangers lie on the horizon? It seems as though the answers rely
significantly upon security and the effect of globalization on American cities,
and thus skyscrapers. “The 2001 9/11 is significant because it fundamentally
questioned the prevailing sense of security[33]”
in the United States. Although the U.S. had enjoyed long term success in its past
with security measures, essentially dating back to the attack on Pearl Harbor
in 1941, “the shock experience of 9/11 was linked to a fundamental breach of
security… Security had come to be associated with the integrity and sovereignty
of the nation-state,” and had begun to be taken for granted by both citizens
and the government[34] Thankfully,
since 9/11 the nation and its government have responded adequately, and
security expenditures have increased by 12%[35],
a reasonable amount considering the gaps present in the security of pre 9/11
America. As Mr. Glaeser asserts in Cities
and Warfare, however, one might see 9/11 as the “underside of globalization
- made possible by permeable borders, highly interdependent economies, loose
multinational corporate structures, and powerful but vulnerable cities.”[36]
It
is inherently true that the world has become a global market. Tourism has
increased on an international scope. Nations across the globe have come to rely
on each other for reserves and requirements, such as oil, and economies like
those seen in the United States have shipped jobs to overseas markets to allow
for greater efficiency of production at lower labor costs than can be achieved
on the home front. The problem has become that “the very same forces of
globalization that increased tourism, the transfer of capital, and the
importance of cities, [has] also paved the way for increased terror.”[37]
H.V. Savitch further explains this idea in the following quote:
Although globalization has made
cities vital nodes of the international economy, it also has made them highly
prized targets of attack. Office towers, hotels, theaters, legislative houses,
embassies, and monuments are symbols of the new economy and of Western power.
Hitting them with bombs, explosives, or bullets would give terrorists
international notoriety (or, for some, acclaim) and guarantee a global
audience. More pedestrian urban sites such as marketplaces, nightclubs, buses,
and subways are targeted to intimidate whole populations and paralyze normal
life. Moreover, unlike military bases that are hardened with radar, missiles,
and guards, cities are open, unprotected, and considered to be “soft” targets.
Although the positive side of globalization emphasizes the city’s strength and
resilience, the negative side exploits its vulnerability and fragility.[38]
This sort of thought
gives the logical impression that the future successfulness of cities will rely
nearly exclusively on the effects of globalization, both the good and the bad.
Cities, and skyscrapers, could conceivably achieve wonderful future economic
success, but continued attacks could also cause great changes to need to occur.
If terrorist attacks would continue to occur, the long term impact of the
destruction of buildings seems to depend on whether the demand for physical
space in the area is such that the buildings would be rebuilt. If the price of
space after the destruction is not high enough to cover the costs of new
construction, then the impact of the attack will be permanent.[39]
The demand for space in the high profile American cities, such as New York
City, Chicago, and Los Angeles, is such that it is hard to consider any future
moment in time when either the danger in those cities would become so high that
building became undesirable, or that the future construction in an area would
be such that it could not cover the costs of the destruction, at least in a
recuperation over time.
The largest future threats to both
cities and skyscrapers, though, are present in methods which have not yet been
used in large scales, at least in the United States. Bio-terror and chemo-terror
are two relatively new methods of terrorist attacks which will likely be used
more in the future. A “dirty bomb” consists of conventional explosives covered
with radioactive material, and would cause mass destruction, poisoning people,
destroying buildings, and causing widespread panic.[40]
As can be imagined, such panic could easily be brought to heavily populated
areas such as Washington D.C., Chicago, or New York City if a dirty bomb was
utilized as an act of terror. Even more so, this type of bomb could cause mass
chaos in a skyscraper. The largest problems in skyscrapers, even with fires
which they are designed to handle, tend to be deal with poor ventilation. This
typically results in smoke inhalation for the users of the building, which can
cause a large number of fatalities. An attack utilizing a dirty bomb could
poison the great majority of those within a skyscraper, causing far greater
percentages of casualties than in any other method of attack known today.
The
amount of destruction caused by the attacks of September 11th is
undeniable. “The estimated economic loss to New York City came to $83 billion
in damages and around 125,000 in jobs.”[41]
One year after the attacks, the hotel occupancy rate was still down by more
than 10%, and an estimated 83,000 jobs had disappeared from the New York
metropolitan area.[42]
Scholars around the globe questioned the perseverance of American cities and
skyscrapers, and their ability to stay afloat after such a brutal attack. Some
critics even went so far as to label the skyscraper a failed venture. Over
time, cities have undoubtedly absorbed the bulk of terror assaults, and they will
likely be the front on which the terrorism conflict continues due to the nature
of the crime. American cities will continue to prosper, though, even if in the
face of danger. Jerusalem and London have shown the United States that such
attacks cannot permanently stunt the grown of urban centers. The great visible
life form of the great American cities will continue to flourish as well.
Despite the attacks of September 11th, skyscrapers continue to be
built at a rapid rate, including those which fall into the category of super
tall. Although these structures likely become immediate targets of terrorism,
including all of its ugly, new methods such as bio-terror and chemo-terror,
they simply cannot be kept down forever because of the vast economic possibilities
such structures can provide to the cities which house them. The terrorist
attacks of September 11th, 2001 did shatter the steel of the World
Trade Center Towers and the Pentagon, and shook the fundamental foundations of
the great buildings of America, but they absolutely could not break the will or
the steel resolve of the American people, and of American cities.
|
Building
|
City
|
Height (m)
|
|
Burg Dubai
|
Dubai
|
705
|
|
Russia Tower
|
Moscow
|
648
|
|
International Business Center
|
Seoul
|
580
|
|
Freedom Towe
|
New York
|
541
|
|
Trump International Hotel and Tower
|
Chicago
|
343
|
|
Trump International Hotel and Tower
|
Toronto
|
325
|
|
Waterview Tower
|
Chicago
|
314
|
|
London Bridge Tower
|
London
|
305
|
|
|
|
|
Source: Emporis Corporation (2004)
Figure 2: Approved super-tall buildings (September
2001–September 2004)[44]
Works Cited
Bleiker, Roland. "Art After 9/11." Alternatives: Global, Local,
Political 31, no. 1 (January
2006): 77-99. JSTOR.
Charney, Igal. "Reflections on the Post-WTC
Skyline: Manhattan and Elsewhere." International
Journal of Urban and Regional Research 291
(March 2005): 172-79. Google Scholar.
Fuerst, Franz. "Exogenous Shocks and Real
Estate Rental Markets: An Event Study of the 9/11 Attacks and their Impact on
the New York Office Market." (2003): 1-22. Google Scholar.
Glaeser, Edward L., and Jesse M. Shapiro.
"Cities and Warfare: The Impact of Terrorism on Urban Form." Urban Economics Symposium (November 30, 2001): 1-30. Google
Scholar.
Kunstler, J H., and N A. Salingaros. "The
End of Tall Buildings." Planetizen (2003).
Miller, Norman G., Sergey Markosyan, Andrew Florance,
Brad Stevenson, and Hans Op't Veld. "The 9/11/2001 Impact on Trophy and
Tall Office Property." Journal
of Real Estate Portfolio Management (2003):
107-25. Google Scholar
Savitch, H. V., Ardashev "Does 9-11 Portend
a New Paradigm for Cities." Urban
Affairs Review 39, no. 1
(September 2003): 103-27. Google Scholar
Savitch, H. V., Ardashev "Does 9-11 Portend
a New Paradigm for Cities." The
Economist, September 2003.
The White House. "The War on Terrorism: At
Home and Abroad Frequently Asked Questions." 2003. http://georgewbush-whitehouse.archives.gov/infocus/nationalsecurity/faq-what.html.
U.S. State Department. 1999. Background
information on foreign terrorist organizations. Washington, DC: Office of
Counterterrorism.1993-2002. Patterns of global terrorism 1993-2001. Washington,
DC: Office of the Coordinator for Counterterrorism.
[1] U.S. State
Department, “Patterns of Global Terrorism “Background
Information on Foreign Terrorist Organizations, (1999) within H. V. Savitch, “Does 9-11 Portend a New
Paradigm for Cities,” Urban Affairs
Review, vol. 39 (September 2003). p. 103-27
[2] The White House,
“The War on Terrorism: At Home and Abroad, Frequently Asked Questions,” http://georgewbush-whitehouse.archives.gov/infocus/nationalsecurity/faq-what.html
[3] Norman G. Miller, “The 9/11/2001 Impact on
Trophy and Tall Office Property,” Journal
of Real Estate Portfolio Management, (2003). p. 107-25
[4] Miller, p. 107
[5] Igal Chamey, “Reflections on the Post-WTC
Skyline: Manhattan and Elsewhere,” International
Journal of Urban and Regional Research, vol. 291 (2003). p. 1-22
[6] Chamey, p. 172
[7] Chamey, p. 172
[9] Chamey, p. 172
[10] Chamey, p. 173
[11] Edward L. Glaeser, “Cities and Warfare:
The Impact of Terrorism on Urban Form,” Urban
Economics Symposium, (November, 2001). p. 1-30
[12] Glaeser, p. 2
[13] Glaeser, p. 8
[14] Glaeser, p. 8-9
[15] Savitch, p. 108
[16] Savitch, p. 109
[17] U.S. State
Department within Savitch, p. 109
[18] Chamey, p. 173
[19] Miller, p. 112
[20] Glaeser, p. 18
[21] Savitch, p. 114
[22] Savitch, p. 115
[23] Savitch, p. 117
[24] Savitch, p. 118
[25] Savitch, p. 119
[26] Miller, p. 108
[27] Miller, p. 110
[28] Franz Fuerst, “Exogeneous Shocks and real
Estate Rental Markets: An Event Study of the 9/11 Attacks and their Impact on
the New York Office Market,” (2003). p. 107-25
[29] Roland Bleiker, “Art After 9/11,” Alternatives Global, Local, Political,
vol. 31 (January 2006). p. 77-99
[31] Fuerst, p. 10
[32] Chamey, p. 174
[33] Bleiker, p. 79
[34] Bleiker, p. 79
[35] Savitch, p. 115
[36] Glaeser, p. 106
[37] Savitch, p. 107
[38] Savitch, p. 107
[39] Glaeser, p. 13
[40] Savitch, p. 109
[41] Savitch, p. 113-114
[42] Savitch, p. 114
[43] Fuerst, p. 22
[44] Chamey, p. 174
