Ryga, George
General Publishing Co., 1982
Buku Teks
Beal, George M.
Iowa State University Press , 1962
Buku Teks
Troxell, George Earl
McGraw-Hill, 1968
Buku Teks
Salomon, Pierre
Paris Hatier-Boivin 1953
Buku Teks
Farmer, Albert John
British Council by Longmans, Green, 1966
Buku Teks