Παραπομπή σε μορφή APA (7η εκδ.)

Gray, E., & O'Sullivan, N. (2003). Practice Tests for the PET 1 Preliminary English Test: Student's Book. Express Publishing.

Παραπομπή σε μορφή Chicago (17η εκδ.)

Gray, Elisabeth, και Neil O'Sullivan. Practice Tests for the PET 1 Preliminary English Test: Student's Book. Newbury: Express Publishing, 2003.

Παραπομπή σε μορφή MLA (8th εκδ.)

Gray, Elisabeth, και Neil O'Sullivan. Practice Tests for the PET 1 Preliminary English Test: Student's Book. Express Publishing, 2003.