PONGSTHORN , C., H. OZAWA, T. AIZAWA, T. KUSAKABE, T. NAKAMURA, and E. ITOI. “Giant Sacral Schwannoma: A Report of Six Cases”. Upsala Journal of Medical Sciences, vol. 115, no. 2, Nov. 2009, pp. 146–152, doi:10.3109/03009730903359674.