Cita APA (7a ed.)

Van Ek, J., & Alexander, L. (1988). Threshold level english in a european unit/credit system for modern language learning by adults. Longman.

Cita Chicago Style (17a ed.)

Van Ek, J.A, y L.G Alexander. Threshold Level English in a European Unit/credit System for Modern Language Learning by Adults. London: Longman, 1988.

Cita MLA (9a ed.)

Van Ek, J.A, y L.G Alexander. Threshold Level English in a European Unit/credit System for Modern Language Learning by Adults. Longman, 1988.