1. M. Jackson, “Semilattices with closure,” Algebra Universalis 52 (1), 1–37 (2004).
2. C. Lutz and F. Wolter, “Mathematical logic for life science ontologies,” in Logic, Language, Information, and Computation, Lecture Notes in Comput. Sci. (Springer, Berlin, 2009), Vol. 5514, pp. 37–47.
3. F. Baader, R. Küsters, and R. Molitor, “Computing least common subsumers in description logics with existential restrictions,” in Proceedings of the 16th International Joint Conference on Artificial Intelligence (IJCAI’99) (Morgan Kaufmann, 1999), pp. 96–101.
4. SNOMED,
http://www.ihtsdo.org/snomed-ct.
5. L. D. Beklemishev, “Provability algebras and proof-theoretic ordinals. I,” Ann. Pure Appl. Logic 128 (1-3), 103–123 (2004).