1. Contraction ring as a cause of dystocia;White;Proc R Soc Med,1912
2. Constriction ring dystocia;Rudolph;J Obstet Gynaec Br Emp,1935
3. Constriction ring dystocia;Rudolph;JAMA,1937
4. Diagnosis and treatment of constriction ring dystocia;Uszynski;Ginekol Pol,1980