Cita APA (7a ed.)

Ek, J. A. v., & Alexander, L. G. (1991). The threshold level: For modern language learning in schools (1st published, 8th imp.). Longman.

Cita Chicago Style (17a ed.)

Ek, Jan Ate van, y L. G. Alexander. The Threshold Level: For Modern Language Learning in Schools. 1st published, 8th imp. [S.l.]: Longman, 1991.

Cita MLA (9a ed.)

Ek, Jan Ate van, y L. G. Alexander. The Threshold Level: For Modern Language Learning in Schools. 1st published, 8th imp. Longman, 1991.