Merriam-Webster, Incorporated, 1996
Multimedia
William Allan Neilson, editor in chief; Thomas A. Knott, general editor; Paul W. Carhart, managing editor
Springfield, G & C Merriam Co.
Buku Referensi
Encyclopaedia Britannica, 1981
Buku Referensi
Encyclopaedia Britannica, 1981
Buku Referensi
Encyclopaedia Britannica, 1981
Buku Referensi