Egbert, Lawrence Deems
Oceana, 1979
Buku Referensi
Morales-Macedo, Fernando
Alphen Aan den Rijn, 1979
Buku Teks
Williams, Edwin B., author
Holt, Rinehart and Winston, [Date of publication not identified]
Buku Referensi
Vollnhals, Otto, author
Routledge, 1992
Buku Referensi
Routledge, 1997
Buku Referensi