Cita APA (7a ed.)

Kleefstra, W. J. (1980). The concept of data model in database systems. s.n.].

Cita Chicago Style (17a ed.)

Kleefstra, Willem Johannes. The Concept of Data Model in Database Systems. [S.l.: s.n.], 1980.

Cita MLA (8a ed.)

Kleefstra, Willem Johannes. The Concept of Data Model in Database Systems. s.n.], 1980.