1. Williams obstetrics;Cunningham,2010
2. Myles textbook for midwives,2014
3. Oxorn-Foote human labor & birth;Posner,2013
4. ACOG practice bulletin: shoulder dystocia. Number 40, November 2002. (Replaces practice pattern number 7, October 1997);Sokol;Int J Gynaecol Obstet,2003
5. Shoulder dystocia,2012