Cita APA (7a ed.)
(1991). Collins Cobuild Student's Grammar: Practice Material by Dave Willis. Self-study Edition with Answer Key. HarperCollins Publishers Ltd.
Cita Chicago Style (17a ed.)
Collins Cobuild Student's Grammar: Practice Material by Dave Willis. Self-study Edition with Answer Key. London: HarperCollins Publishers Ltd, 1991.
Cita MLA (9a ed.)
Collins Cobuild Student's Grammar: Practice Material by Dave Willis. Self-study Edition with Answer Key. HarperCollins Publishers Ltd, 1991.
Precaución: Estas citas no son 100% exactas.