Gray, E., & O'Sullivan, N. (2003). Practice Tests for the PET 1 Preliminary English Test: Teacher's Book. Express Publishing.
Chicago-referens (17:e uppl.)Gray, Elisabeth, och Neil O'Sullivan. Practice Tests for the PET 1 Preliminary English Test: Teacher's Book. Newbury: Express Publishing, 2003.
MLA-referens (8:e uppl.)Gray, Elisabeth, och Neil O'Sullivan. Practice Tests for the PET 1 Preliminary English Test: Teacher's Book. Express Publishing, 2003.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.