Ewing, J.H.
Student Outline Co. , 1960
Buku Teks
Wilkes, Angela
Passport Books, [Date of publication not identified]
Buku Teks SO
Wilkes, Angela
Passport Books, 1987
Buku Teks SO
Wilkes, Angela
Chicago: A Division of NTC Pub., 1987,
Buku Referensi
Gordon, W. Terrence
Writer and Readers Pubishing, 1996
Buku Teks SO