^ Yamanaka, Naoya; Okayama, Tomoaki; Oishi, Shin’ichi (2016). “Verified error bounds for the real gamma function using double exponential formula over semi-infinite interval”. Mathematical Aspects of Computer and Information Sciences: 6th International Conference, MACIS 2015, Berlin, Germany, November 11-13, 2015, Revised Selected Papers 6 (Springer International Publishing): 224-228. doi:10.1007/