source: http://delivery.acm.org/10.1145/2380000/2371297/p20-casestudy.pdf?ip=91.180.55.48&id=2371297&acc=OPEN&key=4D4702B0C3E38B35%2E4D4702B0C3E38B35%2E4D4702B0C3E38B35%2E6D218144511F3437&__acm__=1555347214_b842576bc6891c4c77d0be819a0348e4