J. W. de Bakker Willem P. de Roever Grzegorz Rozenberg Foundations of Object-Oriented Languages, REX School/Workshop, Noordwijkerhout, The Netherlands, May 28 - June 1, 1990, Proceedings REX Workshop Lecture Notes in Computer Science 489 Springer 1991 3-540-53931-X https://doi.org/10.1007/BFb0019438 db/conf/rex/rex90.html