1. Campbell MF (1979) In: Harrison JH, Gittes RF, Permutter AD (eds) Campell's urology, 4th edn, vol. 2. Saunders, London, pp 1481?1542
2. Stowens D (1959) Pediatric pathology, Williams and Wilkins, Baltimore
3. Stoll C, Roth MP, Dott B, Bigel P (1984) Etude des malformations congénitales dans le Nord de l'Alsace. Méd Hyg 42: 505?512
4. SAS (1987) SAS/STAT TM Guide for personal computers, 6th edn. SAS Institute, Cary, N.C., pp 773?875
5. Berry CA, Chantler C (1986) Urogenital malformations and disease. Br Med Bull 42: 181?186