APA (7th ed.) Citation

Bell, B. (1960). On the structure of the sunspot zone. Smithsonian Institution.

Chicago Style (17th ed.) Citation

Bell, Barbara. On the Structure of the Sunspot Zone. Washington, D.C.: Smithsonian Institution, 1960.

MLA (9th ed.) Citation

Bell, Barbara. On the Structure of the Sunspot Zone. Smithsonian Institution, 1960.