1. Congenital valves of the posterior urethra;Beard,1952
2. Urethral Lesions in Infancy and Childhood;Burrows,1965
3. Anomalies of the genital tract;Campbell,1951
4. Congenital valves of the posterior urethra;Counseller;J. Urol.,1935
5. Congenital urethral valves;Emmett,1964