Longman Cheshire, 1991
Buku Teks
Ebenstein, William, author
Prentice-Hall, 1967
Buku Teks
Lnge, Oscar
Warsawa Polonia Publishing House 1957
Buku Teks
Ebenstein, William, author
Prentice-Hall, 1954
Buku Teks
London : Central Books Ltd
Majalah, Jurnal, Buletin