Zafar Ali , Jaweria Riaz , Mahwash Rashid. “Skeletal and Extra Skeletal Ewing’s Sarcoma / Primitive Neuroectodermal Tumors(PNET): Clinicopathological Study”. Journal of Rawalpindi Medical College, vol. 16, no. 2, Dec. 2012, http://journalrmc.com/index.php/JRMC/article/view/574.