APA (7th ed.) Citation

Welmers, W. E., & Welmers, B. F. (1968). Igbo: A learner's manual. [Selbstverl. des 1. Verf.].

Chicago Style (17th ed.) Citation

Welmers, William Everett, and Beatrice F. Welmers. Igbo: A Learner's Manual. Los Angeles: [Selbstverl. des 1. Verf.], 1968.

MLA (9th ed.) Citation

Welmers, William Everett, and Beatrice F. Welmers. Igbo: A Learner's Manual. [Selbstverl. des 1. Verf.], 1968.