References
- Greenhill I.P. Principles and Practice of Obstetricsp. Philadelphia and London 1955; 464
- Jaggard W.W., De Lee J.B. Principles and Practice of Obstetricsp. Philadelphia and London 1933; 498, cited from
- Leroux De Lee J.B. Principles and Practice of Obstetrics. Philadelphia and London 1933; 499, cited from