U.S. Bureau of the Census . (1991). Statistical abstract of the United States. Washington DC: U.S. Government Printing Office.
8.
U.S. Travel Data Center . (1989). Discover America 2000. Washington, DC: Travel Industry Association of America.
9.
U.S. Travel Data Center . (1990). The mature market. Washington, DC: Travel Industry Association of America.
10.
U.S. Travel Data Center . (1991). Tourism works for America. Washington, DC: National Travel and Tourism Awareness Council.
11.
U.S. Travel Data Center . (1992). 1992 outlook for travel and tourism. Washington, DC: Author.
12.
Waters, S. (1991). Travel industry world yearbook. New York: Child & Waters, Inc.
13.
Wharton Econometric Forecasting Associates . (1991). The WTTC report: Travel and tourism in the world economy. New York: World Travel and Tourism Council.