Eckholm, Erik P.
W.W. Norton, 1976
Buku Teks SO
Academy Group, 1995
Buku Referensi
Chukovsky, Nikolai
Foreign Languages Publishing House , [Date of publication not identified]
Buku Teks SO
Fish, Donald
G.P. Putnam's Sons , 1962
Buku Teks
Carr, Herman Y.
McGraw-Hill, 1971
Buku Teks SO