Thorne, Kaye, author
Crest publishing, 1999
Buku Referensi
Johannsen, Hano, author
Crest Publishing House, 1999
Buku Referensi
Ho, Samuel K., author
Crest publishing, 1999
Buku Referensi
Seekings, David, author
Crest publishing, 1999
Buku Referensi
Anmol Publications PVT, 1999
Buku Teks