Ullman, J. D. (1989). Principles of database and knowledge-base systems. Computer Science Press.
Lua i Stíl Chicago (17ú heag.)Ullman, Jeffrey D. Principles of Database and Knowledge-base Systems. Rockville, MD: Computer Science Press, 1989.
Lua MLA (9ú heag.)Ullman, Jeffrey D. Principles of Database and Knowledge-base Systems. Computer Science Press, 1989.
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