King, George E (2012), Hydraulic fracturing 101 (PDF), Society of Petroleum Engineers, SPE 152596 – via Kansas Geological Survey Staff.
2016년 5월 31일에 확인함.  King, George E (2012), 《Hydraulic fracturing 101》 (PDF), Society of Petroleum Engineers, SPE 152596 – Kansas Geological Survey 경유  Staff.