Gore, M.S., author
Asia Publishing House, 1965
Buku Teks
Cohen, Nathan Edward, author
National Ass. of Workker, 1964
Buku Teks
Nicolson, Paula, author
MacMillan Education, 1986
Buku Teks
Bedford Square Press, 1982
Buku Teks
Brayne, Hugh, author
Blackstone Press, 1991
Buku Teks