On a theory of decision problems in programming languages

Hans Langmaack. On a theory of decision problems in programming languages. In Edward K. Blum, Manfred Paul, Satoru Takasu, editors, Mathematical Studies of Information Processing, Proceedings of the International Conference, Kyoto, Japan, August 23-26, 1978. Volume 75 of Lecture Notes in Computer Science, pages 538-558, Springer, 1978.