Παραπομπή APA

Ruggieri, D. D. (1969). Secrets of the sky. Hamlyn.

Παραπομπή Chicago Style

Ruggieri, Deryck D. Secrets of the Sky. London: Hamlyn, 1969.

Παραπομπή MLA

Ruggieri, Deryck D. Secrets of the Sky. Hamlyn, 1969.