Cita APA (7a ed.)

Walker, E., & Elsworth, S. (1998). Grammar practice for elementary students.

Cita Chicago Style (17a ed.)

Walker, Elaine, y Steve Elsworth. Grammar Practice for Elementary Students. Harlow, 1998.

Cita MLA (9a ed.)

Walker, Elaine, y Steve Elsworth. Grammar Practice for Elementary Students. 1998.