Cambridge University Press, 2010
eBooks
Washington : Pan American Union, General Secretariet of the Organization of American States
Majalah, Jurnal, Buletin
Smith, Karl J.
Brooks/Cole, 1973
Buku Teks SO
Ueda, Makota
Stanford University Press, 1976
Buku Teks SO
Singapore Archipelago Press 1996,
Buku Referensi