Pylee, M.V.
Asia Publishing House, 1960
Buku Teks
Hardgrave, Robert L., author
Harcourt, Brace, 1970
Buku Teks
Sharan, P.
Metropolitan, 1984
Buku Teks
Hardgrave, Robert L., author
Harcourt College, 2000
Buku Teks
Goetz, Hermann, author
Grown, 1959
Buku Referensi