Pearman, William A. and Starr, Philip
New York : Garland Publishing, 1988,
Buku Referensi
Carlson, Rick
The Mosby , 1987
Buku Teks
Mooney, Gavin H.
Harvester Wheatsheaf, 1994
Buku Teks
Saltman, Deborah
Harcourt Brace Jovanovich, 1991
Buku Teks
edited by Fiona Sim, Martin McKee
McGraw-Hill, 2011
Buku Teks