Gray, E., & O'Sullivan, N. Practice Tests for the PET 1 Preliminary English Test: Class CDs. Express Publishing.
Chicago-Zitierstil (17. Ausg.)Gray, Elisabeth, 与 Neil O'Sullivan. Practice Tests for the PET 1 Preliminary English Test: Class CDs. Newbury: Express Publishing.
MLA-Zitierstil (8. Ausg.)Gray, Elisabeth, 与 Neil O'Sullivan. Practice Tests for the PET 1 Preliminary English Test: Class CDs. Express Publishing.
警告：这些引文格式不一定是100％准确.