Ziegler, Kathleen, author
Rockport Publishers, 1994
Buku Referensi
Drago, Carl, author
Blackwell, 2014
Buku Teks
Jackson, Paul, author
Chancellor, 1994
Buku Referensi
Alfaro-LeFevre, Rosalinda, author
Lippincott , 1998
Buku Teks
Atkinson, Jennifer L., author
Rockport, 1996
Buku Teks