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