1. Automatic Information Organization and Retrieval;Salton,1968
2. Rough classification;Pawlak;Int. J. Man-Mach. Stud.,1984
3. Domains for denotational semantics;Scott,1982
4. An algebraic approach to information retrieval systems;Ras;Int. J. Comp. Inf. Sci.,1982
5. Classification of objects by means of attributes;Pawlak,1981