@incollection{BerghammerEhlerMoeller1990,
  author    = {Rudolf Berghammer and Herbert Ehler and Bernhard M{\"o}ller},
  title     = {On the refinement of nondeterministic recursive routines by transformation},
  booktitle = {Programming concepts and methods: proceedings of the IFIP Working Group 2.2/2.3 Working Conference on Programming Concepts and Methods, Sea of Galilee, Israel, 2 - 5 April, 1990},
  editor    = {Manfred Broy and C. B. Jones},
  isbn      = {0-444-88545-5},
  year      = {1990},
}