A. Flögel, H. Kleine Büning, and T. Lettmann, “On the restricted equivalence for subclasses of propositional logic,” RAIRO - Theoretical Informatics and Applications, pp. 327–340, 1993.
LibreCat: /record/19814
DOI: 10.1051/ita/1993270403271

B. I. Dahn, T. Lettmann, and W. Schönfeld, ILFA Interface Concept, vol. 193. ´Heidelberg: Wissenschaftliche Zentrum der IBM Deutschland , 1991.
LibreCat: /record/19822

H. Kleine Büning, T. Lettmann, and E. W. Mayr, “Projections of vector addition system reachability sets are semilinear,” Theoretical Computer Science, pp. 343–350, 1989.
LibreCat: /record/19818
DOI: 10.1016/0304-3975(89)90055-8

H. Kleine Büning and T. Lettmann, “Perspektiven für die Logikprogrammierung,” in Workshop Wissensrepräsentation in Expertensystemen, 1988, pp. 56–78.
LibreCat: /record/19820

H. K. Büning and T. Lettmann, “Representation independent query and update operations on propositional definite Horn formulas,” in Computation Theory and Logic, E. Börger, Ed. Berlin, Heidelberg, 1987, pp. 208–223.
LibreCat: /record/19821
DOI: 10.1007/3-540-18170-9_167

H. Kleine Büning and T. Lettmann, “Classes of first order formulas under various satisfiability definitions,” in 8th International Conference on Automated Deduction, Berlin, Heidelberg, 1986.
LibreCat: /record/19819
DOI: 10.1007/3-540-16780-3_119