1. Adámek, J., Herrlich, H., Strecker, G.: Abstract and Concrete Categories. Wiley, New York (1990)
2. Baumeister, H.: Relations between Abstract Datatypes modeled as Abstract Datatypes. PhD thesis, Universität des Saarlandes (1998)
3. Bergstra, J.A., Heering, J., Klint, P.: Module algebra. Journal of the ACM 37, 335–372 (1990)
4. Lecture Notes in Computer Science,2004
5. Borzyszkowski, T.: Logical systems for structured specifications. Theoretical Computer Science 286, 197–245 (2002)