Barth, Peter Programming Logics, MPI for Informatics, Max Planck Society;
https://rdcu.be/dto2f (Verlagsversion)
Barth, P. (1994). Simplifying Clausal Satisfiability Problems. In J.-P. Jouannaud (Ed.), Proceedings of the 1st International Conference on Constraints in Computational Logics (CCL'94) (pp. 19-33). Berlin, Germany: Springer.