1. Arey, L. B.: Developmental Anatomy. A textbook and laboratory manual of embryology, 7th ed. W. B. Saunders, Philadelphia 1965, pp. 3–12.
2. Cheng, Yang Chang: Anterior urethral valves: a case report.J. Urol. 100, 29 (1968).
3. Cobb, B. G., Wolff, J. A., Ansell, J. S.: Congenital stricture of the proximal urethral bulb.J. Urol. 99, 629 (1968).
4. Grasset, D.: Obstructions au bas appareil urinaire.J. d'Urol. et Néphrol. 76, 1 (1970).
5. Johansen, B.: Reconstruction of the male urethra in strictures.Acta Chir. Scand. Suppl. 176 (1953).