Initial Algebraic Semantics for Non Context-Free Languages. - Heinz Kaphengst; Horst Reichel (FCT, 1977)

What is Computable for Abstract Data Types? - Heinz Kaphengst (FCT, 1981)

Zum Aufbau Einer Mehrsortigen Elementaren Logik. - Heinz Kaphengst (Math. Log. Q., 1985)