On the restricted equivalence for subclasses of propositional logic
A. Flögel, H. Kleine Büning, T. Lettmann, RAIRO - Theoretical Informatics and Applications (1993) 327–340.

ILFA Interface Concept
B.I. Dahn, T. Lettmann, W. Schönfeld, ILFA Interface Concept, Wissenschaftliche Zentrum der IBM Deutschland , ´Heidelberg, 1991.

Projections of vector addition system reachability sets are semilinear
H. Kleine Büning, T. Lettmann, E.W. Mayr, Theoretical Computer Science (1989) 343–350.

Perspektiven für die Logikprogrammierung
H. Kleine Büning, T. Lettmann, in: G. Rahmstorf (Ed.), Workshop Wissensrepräsentation in Expertensystemen, Berlin, Heidelberg, 1988, pp. 56–78.

Representation independent query and update operations on propositional definite Horn formulas
H.K. Büning, T. Lettmann, in: E. Börger (Ed.), Computation Theory and Logic, Berlin, Heidelberg, 1987, pp. 208–223.