Gray, E., & O'Sullivan, N. (2003). Practice Tests for the PET 1 Preliminary English Test: Student's Book. Express Publishing.
Chicagoスタイル(17版)引用形式Gray, Elisabeth, , Neil O'Sullivan. Practice Tests for the PET 1 Preliminary English Test: Student's Book. Newbury: Express Publishing, 2003.
MLA(8版)引用形式Gray, Elisabeth, , Neil O'Sullivan. Practice Tests for the PET 1 Preliminary English Test: Student's Book. Express Publishing, 2003.
警告: この引用は必ずしも正確ではありません.