MacCurdy, Raymond R
New York Twayne c1968
Buku Teks
Hocleitner, Ricardo Diez
UNESCO, 1978
Buku Teks
Walls, Alfonso Vasseur, author
Mexico Diana S.A. 1963
Buku Referensi
Berlin Hodder and Stoughton 1966
Buku Referensi
London; Cassell LTD., 1978
Buku Referensi