@book{
  author = "Bulgarian Summer School on Mathematical Problems of Quantum Field Theory, Doebner, Heinz Dietrich, 1931-, Palev, Tchavdar D., 1936-",
  title = "Twistor geometry and non-linear systems : review lectures given at the 4th Bulgarian Summer School on Mathematical Problems of Quantum Field Theory, held at Primorsko, Bulgaria, September 1980",
  year: 1982
  key = "Twistor theory--Congresses",
  key = "Nonlinear theories--Congresses",
  key = "Quantum field theory--Congresses",
  publisher = "Springer-Verlag",
  address = "Berlin ; New York",
  series = "Lecture notes in mathematics ; 970",
  ISSN/ISBN = "9783540119722 [3540119728] (: Berlin)",
  ISSN/ISBN = "9780387119724 [0387119728] (: New York)",
}