“Agile development methodologies promise higher customer satisfaction, lower defect rates, faster development times and a solution to rapidly changing requirements. Plan-driven approaches promise predictability, stability, and high assurance. However, both approaches have shortcomings that, if left unaddressed, can lead to project failure. The challenge is to balance the two approaches to take advantage of their strengths and compensate for their weaknesses.”

Grady Booch (1986) Software Engineering with Ada p. 220. cited in: David J. Gilmore et al. (1994) User-Centred Requirements for Software Engineering Environments. p. 108

As quoted in Conversations with I. M. Pei : Light Is the Key (2000) by Gero von Boehm, p. 113

United Nations, Sri "Lanka urges UN to study global inequality, failure to lift millions out of poverty" http://www.un.org/apps/news/story.asp/html/story.asp?NewsID=45978&Cr=general+assembly&Cr1=, 24 September 2013.

Source: Software Engineering: Principles and Practice, 2007, p. 2

Source: Gulzarilal Nanda: A Life in the Service of the People, p.32.

Source: Lateral Thinking : Creativity Step by Step (1970), p. 29.
Context: With vertical thinking one may look for different approaches until one finds a promising one. With lateral thinking one goes on generating as many approaches as one can even after one has found a promising one. With vertical thinking one is trying to select the best approach but with lateral thinking one is generating different approaches for the sake of generating them.

1960s, Freedom From The Known (1969)
Context: The world accepts and follows the traditional approach. The primary cause of disorder in ourselves is the seeking of reality promised by another; we mechanically follow somebody who will assure us a comfortable spiritual life. It is a most extraordinary thing that although most of us are opposed to political tyranny and dictatorship, we inwardly accept the authority, the tyranny, of another to twist our minds and our way of life. So if we completely reject, not intellectually but actually, all so-called spiritual authority, all ceremonies, rituals and dogmas, it means that we stand alone and are already in conflict with society; we cease to be respectable human beings. A respectable human being cannot possibly come near to that infinite, immeasurable, reality.

Tom DeMarco and Barry Boehm. " The agile methods fray http://cf.agilealliance.org/articles/system/article/file/872/file.pdf." Computer 35.6 (2002): 90-92.