Cexhead, Elizabeth
Longmans Green, 1961
Buku Teks
Stone, Richard
Blackstone Press limited, 1997
Buku Teks
McDowell, Linda, 1949-, author
Wiley-Blackwell, 2013
Buku Teks
edited by Violet B. Haas, Carolyn C. Perrucci
The University of Michigan Press, 1984
Buku Teks
Carr-Saunders, A. M., author
Clarendon Press, 1933
Buku Teks