Dahl, O.-J. and Nygaard, K. "Class and subclass declarations"

Buxton, J. (1968) Buxton, J. ed.: Simulation Programming Languages. Proceedings from the IFIP Working Conference in Oslo, May 1967, North Holland, 1968.   Ole-Johan Dahl

Languages mentioned SIMULA {1962} SIMUlation LAnguage SIMULA 67 {1967} Object-oriented simulation language