@book{
  author = "Spring School on Superstrings, Green, Michael B.",
  title = "Superstrings '89 : proceedings of the Trieste Spring School, 3-14 April 1989",
  year: c1990
  key = "String models--Congresses",
  key = "Superstring theories--Congresses",
  publisher = "World Scientific",
  address = "Singapore",
  ISSN/ISBN = "9789810201388 [9810201389]",
}