1981
Gregor Engels, Udo Pletat, Hans-Dietrich Ehrich: Handling Errors and Exceptions in the Algebraic Specifications of Data Types. Technical report, no. OSM-I-3. University of Osnabr\"uck (1981)
Udo Pletat, Gregor Engels, Hans-Dietrich Ehrich: Operational Semantics of Algebraic Specifications with Conditional Equations. Technical report, no. 118. University of Dortmund, Department of Computer Science (1981)