Lafosse, Michael G., author
Quarry Books, 1998
Buku Referensi
Ziegler, Kathleen, author
Rockport Publishers, 1994
Buku Referensi
Shannon, Faith, author
Reed International Books, 1987
Buku Referensi
Ferre, John P
Columbus : Charles E. Merril Publishing company,1983,
Buku Referensi
Atkinson, Jennifer L., author
Rockport, 1996
Buku Teks