Cita APA (7a ed.)

Lawrence, J., & Williams, A. (2004). Valid: For batxillerat 1. Burlington.

Cita Chicago Style (17a ed.)

Lawrence, Jane, y Alan Williams. Valid: For Batxillerat 1. Limassol: Burlington, 2004.

Cita MLA (9a ed.)

Lawrence, Jane, y Alan Williams. Valid: For Batxillerat 1. Burlington, 2004.