1. Achache, A. (1982), Galois connection of a fuzzy subset, Fuzzy Sets and Systems, 8, pp. 215–218.
2. Achache, A. (1988), How to fuzzify a closure space, J. Math.l Anal. Appl., 130, pp. 538–544.
3. Barbut, M., Monjardet, B. (1971), Ordre et Classification, Algébre et Combinatoire, Hachette, Paris.
4. Barthélemy, J.P., Leclerc, B., Monjardet, B. (1984a), Ensembles ordonnés et taxonomie mathématique, In Pouzet, M., Richard, M., eds., Orders, descriptions and roles, Annals of Discrete Mathematics, 23, North-Holland, Amsterdam, pp. 523–548.
5. Barthélemy, J.P., Leclerc, B., Monjardet, B. (1984b), Quelques aspects du consensus en classification, in Diday, E., et al., eds., Data Analysis and Informatics III, North- Holland, Amsterdam, pp. 307–316.