1. Cunningham F. G., MacDonald P. C., Gant N. F., Leveno K. J., Gilstrap L. C., III. Williams Obstetrics, 19th edition. Prentice-Hall, London 1993; 371–393, chapter 14
2. Donald I. Practical Obstetric Problems, Fifth edition. Lloyd-Luke Medical, London 1979; 811
3. Long-term ailments due to anal sphincter rupture caused by delivery — a hidden problem
4. Is routine episiotomy necessary?