1. Abiteboul, S., Hull, R., & Vianu, V. (1995). Foundations of databases. Reading, MA: Addison-Wesley.
2. ANSI/X3/SPARC Study Group on Data Base Management Systems (1975). Interim Report. FDT (ACM Sigmod Records), 7(2), 1–140.
3. Arrazola, I., Plainfossé, A., Prade, H., & Testemale, C. (1989). Extrapolation of fuzzy values from incomplete data bases. Information Systems, 14(6), 487–492.
4. Biskup, J. (1981). A formal approach to null values in database relations. In H. Gallaire, J. Minker, & J. Nicolas (Eds.), Advances in Data Base Theory (pp. 299–341). New York, NY: Plenum.
5. Bochvar, D. (1938). Ob odnom trehznachnom iscislenii i ego primenenii k analizu paradoksov klassiceskogo funkcional’nogo iscislenija. Matematiceskij Sbornik, 4, 287–308. English translation: On a three-valued calculus and its applications to the analysis of the paradoxes of the classical extended functional calculus. History and Philosophy of Logic, 2, 87–112, 1981.