Julius Groos Verlag, {s.a}
Majalah, Jurnal, Buletin
Wisconsin : University of Wirconsin Press
Majalah, Jurnal, Buletin
New York : The American Council on the Teaching of Foreign Language Inc
Majalah, Jurnal, Buletin
Donald Freeman and Jack C. Richardsand , author
Cambridge Cambridge University Press 1996
Buku Teks
Gowen, James A., author
McGraw-Hill, 1965
Buku Teks