Mannila, Heikki Algorithms and Complexity, MPI for Informatics, Max Planck Society;
Mehlhorn, Kurt Algorithms and Complexity, MPI for Informatics, Max Planck Society;
Mannila, H., & Mehlhorn, K. (1985). A Fast Algorithm for Renaming a Set of Clauses as a Horn Set. Information Processing Letters, 21(5), 269-272. doi:10.1016/0020-0190(85)90096-1.