Seward, William W., author
Frederick Fell, 1963
Buku Teks
Hilfer, Tony, author
Longman, 1992
Buku Teks
Bingham, Neil, author
Page One Publishing , 2000
Buku Referensi
Webb, Michael, 1937-, author
Uneverse publishing, 2001
Buku Teks
Hamalian, Leo, author
McGraw-Hill, 1967
Buku Teks