Phillips, Ralph W.
United states Government Printing Office, 1945
Buku Teks
Stacy, Ralph W.
Mosby , 1966
Buku Teks
Townsed, Ralph
G.P. Putnam's Sons, 1933
Buku Teks
Didin Hafidhuddin, author
Gema Insani Press, 2002
Buku Teks
Scurfield, Elizabeth, author
NTC Pub. Group, 1992
Buku Teks