Corbetta, Piergiorgio, author
Sage Publications , 2003
Buku Teks
edited by J. Blank and M.J. Krijger
John Wiley & Sons, 1983
Buku Teks
Jordan, James A., author
John Wiley & Sons, 2000
Buku Teks
edited by Mary Feeney
Taylor Graham, 1986
Buku Referensi
Sime, Rodney J., author
Saunders College, 1990
Buku Teks