found:Census 2000 geography glossary, via U.S. Census Bureau WWW site, Mar. 28, 2006:metropolitan area (MA) (a large population nucleus; an MA contains one or more central counties; some MAs are defined around two or more central cities)
found:OMB Bulletin no. 13-01, (Feb. 28, 2013), viewed via WWW Dec. 27, 2013("Revised Delineations of Metropolitan Statistical Areas, Micropolitan Statistical Areas ... ")
found:WorldCat search, Dec. 27, 2013(numerous hits on titles using the term "Metropolitan statistical areas" or "Metropolitan statistical area")