1. Efficient implementation of lattice operations;Aït-Kaci;ACM Trans. Program. Languages and Systems,1989
2. An order-sorted logic for knowledge representation systems;Beierle;Artificial Intelligence,1992
3. Many sorted logic = unsorted logic + control?;Cohn,1986
4. On the appearance of sorted literals: a non substitutional framework for hybrid reasoning;Cohn,1989
5. Completing sort hierarchies;Cohn;Comput. Math. Appl.,1992