Παραπομπή APA

Van Duyn J. (1975). practical system and procedures manual. Reston publishing co.

Παραπομπή Chicago Style

Van Duyn J. Practical System and Procedures Manual. Virginia: Reston publishing co, 1975.

Παραπομπή MLA

Van Duyn J. Practical System and Procedures Manual. Reston publishing co, 1975.