
"Einstein and the Search for Unification", p. 10 https://books.google.com/books?id=rEaUIxukvy4C&pg=PA10, in The legacy of Albert Einstein: a collection of essays in celebration of the year of physics (2007)
as quoted by Michio Kaku, Hyperspace: A Scientific Odyssey Through Parallel Universes, Time Warps, and the 10th Dimension (1995)
Context: String theory is extremely attractive because gravity is forced upon us. All known consistent string theories include gravity, so while gravity is impossible in quantum field theory as we have known it, it is obligatory in string theory.
"Einstein and the Search for Unification", p. 10 https://books.google.com/books?id=rEaUIxukvy4C&pg=PA10, in The legacy of Albert Einstein: a collection of essays in celebration of the year of physics (2007)
[Schwarz, J. H., The early history of string theory and supersymmetry, 2012, https://arxiv.org/abs/1201.0981]
as quoted by John Horgan, The End of Science: Facing the Limits of Knowledge in the Twilight of the Scientific Age (1996)
"Event Horizon" https://web.archive.org/web/20110718030432/http://www.thatsmags.com/shanghai/index.php/article/detail/304/event-horizon (2011)
[The information paradox, arXiv preprint arXiv:hep-th/0612061v2, 14 December 2006, http://arxiv.org/abs/hep-th/0612061] (See also Thorne-Hawking-Preskill bet.)
"The Past and Future of String Theory" in The Future of Theoretical Physics and Cosmology: Celebrating Stephen Hawking's Contributions to Physics (2003) ed. G.W. Gibbons, E.P.S. Shellard & S.J. Rankin
as quoted by John Horgan, The End of Science: Facing the Limits of Knowledge in the Twilight of the Scientific Age (1996)
"Edward Witten" interview, Superstrings: A Theory of Everything? (1992) ed. P.C.W. Davies, Julian Brown
[Why Is Gravity So Elusive? Frank Wilczek, Erik Verlinde, Laura Mersini-Houghton, 4 December 2017, YouTube, https://www.youtube.com/watch?v=7lui9qZ6cDs] 11:20 of 40:44
000.113 http://www.rwgrayprojects.com/synergetics/s00/p0000.html
1970s, Synergetics: Explorations in the Geometry of Thinking (1975), "Synergy" onwards