C. L., Liu; James W., Layland «Scheduling Algorithms for Multiprogramming in a Hard-Real-Time Environment». Journal of the ACM. ACM, 20, 1, gener 1973, pàg. 46–61. DOI: 10.1145/321738.321743. «We define the response time of a request for a certain task to be the time span between the request and the end of the response to that request.»