APA (7th ed.) Citation

Gopsill, F. P. (1987). Interlingua: A course for beginners. British Interlingua Society.

Chicago Style (17th ed.) Citation

Gopsill, F. P. Interlingua: A Course for Beginners. Sheffield, England: British Interlingua Society, 1987.

MLA (9th ed.) Citation

Gopsill, F. P. Interlingua: A Course for Beginners. British Interlingua Society, 1987.