Cita APA (7th ed.)

ABELL, G. O. (1980). Realm of the universe.-- Ed.2. Saunders College.

Cita Chicago (17th ed.)

ABELL, George O. Realm of the Universe.-- Ed.2. Philadelphia: Saunders College, 1980.

Cita MLA (9th ed.)

ABELL, George O. Realm of the Universe.-- Ed.2. Saunders College, 1980.