Cita APA (7a ed.)

Kingsbury, R., & Spratt, M. (1986). Longman proficiency skills. Longman.

Cita Chicago Style (17a ed.)

Kingsbury, Roy, y Mary Spratt. Longman Proficiency Skills. Essex, England: Longman, 1986.

Cita MLA (8a ed.)

Kingsbury, Roy, y Mary Spratt. Longman Proficiency Skills. Longman, 1986.