Cita APA (7a ed.)

Kingsbury, R., & Spratt, M. (1993). Longman proficiency skills: Coursebook (1st pub., 10th impr.). Longman.

Cita Chicago Style (17a ed.)

Kingsbury, Roy, y Mary Spratt. Longman Proficiency Skills: Coursebook. 1st pub., 10th impr. Essex: Longman, 1993.

Cita MLA (9a ed.)

Kingsbury, Roy, y Mary Spratt. Longman Proficiency Skills: Coursebook. 1st pub., 10th impr. Longman, 1993.