University Microfilms International. (1989). Dissertation abstracts international. UMI.
Cita Chicago (17th ed.)University Microfilms International. Dissertation Abstracts International. Ann Arbor, Mich.: UMI, 1989.
Cita MLA (8th ed.)University Microfilms International. Dissertation Abstracts International. UMI, 1989.
Atenció: Aquestes cites poden no estar 100% correctes.