Ambrose, James E., author
John Wiley & Sons, 2005
Buku Teks
Amrose, James, author
John Wiley & Sons, 2000
Buku Teks
Parker, Harry, author
John Wiley & Sons, 1984
Buku Teks
Parker, Harry S., author
John Wiley & Sons, 1991
Buku Teks
prepared by the Special Publications Division, National Geographic Society, Washington, D.C.
The National Geogarphic Society, 1986
Buku Referensi