Gaya APA

Service, P, A, N. (1971). Private and study commercial pilot helicopter ratings ; a study text and guide to the written examination a Zweng manual . North Hollywood: Pan American Navigation Service.

Gaya MLA

Service, Pan, American, Navigation. "Private and study commercial pilot helicopter ratings ; a study text and guide to the written examination a Zweng manual". North Hollywood: Pan American Navigation Service, 1971. Text.