Oxford , Clarendon Press
Buku Referensi
Wessely, J.E., author
Chicago dsb. Pollett Publ. 1946
Buku Referensi
Wichman, K., author
New York, David Mckay Company
Buku Referensi
New York, 1978
Buku Referensi
Wichman, Karl, author
Philadelphia, David McKay Company, 1944
Buku Referensi