Stein, Benno, Oliver Niggemann, and Theodor Lettmann. “Speeding Up Model-Based Diagnosis by a Heuristic Approach to Solving SAT.” In AIA ’06: Proceedings of the 24th IASTED International Conference on Artificial Intelligence and Applications, 273--278, 2006.

Kleine Büning, Hans, and Theodor Lettmann. “Resolution Remains Hard under Equivalence.”https://doi.org/10.1016/s0166-218x(99)00055-4__Discrete Applied Mathematics, 1999, 139–48.https://doi.org/10.1016/s0166-218x(99)00055-4 .

Lettmann, Theodor, and Hans Kleine Büning. Propositional Logicf: Deduction and Algorithms. Cambridge Tracts in Theoretical Computer Science. Cambridge Univ. Press, 1999.

Kleine Büning, Hans, and Theodor Lettmann. “Learning a Representation for Optimizable Formulas.”https://doi.org/10.1007/3-540-61863-5_33__In Lecture Notes in Computer Science. Berlin, Heidelberg, 1996.https://doi.org/10.1007/3-540-61863-5_33 .

Kleine Büning, Hans, and Theodor Lettmann. Aussagenlogik - Deduktion und Algorithmen. Leitfäden und Monographien der Informatik. Teubner, 1994.https://doi.org/10.1007/978-3-322-84809-3 .

Flögel, A., H. Kleine Büning, and Theodor Lettmann. “On the Restricted Equivalence for Subclasses of Propositional Logic.”https://doi.org/10.1051/ita/1993270403271__RAIRO - Theoretical Informatics and Applications, 1993, 327–40.https://doi.org/10.1051/ita/1993270403271 .

Dahn, Bernd I., Theodor Lettmann, and Wolfgang Schönfeld. ILFA Interface Concept. Vol. 193. IWBS Report. ´Heidelberg: Wissenschaftliche Zentrum der IBM Deutschland , 1991.

Kleine Büning, Hans, Theodor Lettmann, and Ernst W. Mayr. “Projections of Vector Addition System Reachability Sets Are Semilinear.”https://doi.org/10.1016/0304-3975(89)90055-8__Theoretical Computer Science, 1989, 343–50.https://doi.org/10.1016/0304-3975(89)90055-8 .

Kleine Büning, Hans, and Theodor Lettmann. “Perspektiven Für Die Logikprogrammierung.” In Workshop Wissensrepräsentation in Expertensystemen, edited by G. Rahmstorf, 56–78. Berlin, Heidelberg, 1988.

Büning, Hans Kleine, and Theodor Lettmann. “Representation Independent Query and Update Operations on Propositional Definite Horn Formulas.”https://doi.org/10.1007/3-540-18170-9_167__In Computation Theory and Logic, edited by Egon Börger, 208–23. Berlin, Heidelberg, 1987.https://doi.org/10.1007/3-540-18170-9_167 .

Kleine Büning, H., and Theodor Lettmann. “Classes of First Order Formulas under Various Satisfiability Definitions.”https://doi.org/10.1007/3-540-16780-3_119__In 8th International Conference on Automated Deduction. Berlin, Heidelberg, 1986.https://doi.org/10.1007/3-540-16780-3_119 .