1. H.D. Ehrich Extensions and Implementations of Abstract Data Type Specifications VIIth MFCS, 1978, Pp. 155–164.
2. H. Ehrig, H.-J. Kreowski, P. Padawitz Stepwise Specification and Implementation of Abstract Data Types Vth ICALP, Udine, 1978.
3. J.A. Goguen, J.W. Thatcher, E.G. Wagner An Initial Algebra Approach to the Specification, Correctness and Implementation of Abstract Data Types IBM Research Report, RC 6487, 1976.
4. H. Klaeren Eine Klasse von Algebren mit struktureller Rekursion und ihre Anwendung bei der abstrakten Software-Spezifikation Dissertation, RWTH Aachen, 1980.
5. J.W. Thatcher, E.G. Wagner, J.B. Wright Data Type Specification: Parameterization and the Power of Specification Techniques 10th STOC, 1978.