Cita APA (7a ed.)

Sheeler, W. D. (1977). Elementary course in english. English Language Service.

Cita Chicago Style (17a ed.)

Sheeler, Willard D. Elementary Course in English. Nueva York: English Language Service, 1977.

Cita MLA (8a ed.)

Sheeler, Willard D. Elementary Course in English. English Language Service, 1977.