1. Cambridge Systematics, Inc. (1996), “Travel Survey Manual”, U.S. Department of Transportation and U.S. Environmental Protection Agency 564 pp.
2. Council of American Survey Research Organization (CASRO) (1982), “On the Definition of Response Rates”, Special Report of the CASRO Task Force on Completion Rates, Lester R. Frankel (Chmn.), 6 pages.