L. Espín, J. Quispe-Alcocer, G. Espín, J. Villacís-Sandoval, and J. Castro-Viteri, “Extraosseous Ewing’s Sarcoma in Spinal Epidural Space”, Int J Med Surg Sci, vol. 3, no. 4, pp. 1003–1007, Dec. 2016.