Zipf, George Kingsley, author
Hafner, 1965
Buku Teks
edited by Gwen Bell
Hawaii University Press, 1976
Buku Teks
Hawley, Amos H., author
The Ronald Press, 1950
Buku Teks
edited by Ian Brownlie, Guy S. Goodwin-Gill
Clarendon Press, 1971
Buku Teks
Centre for Human Right, United Nations , 1991
Buku Teks