Gray, W. S. (1980). Hotel and motel management and operations. Prentice Hall.
Lua i Stíl Chicago (17ú heag.)Gray, William S. Hotel and Motel Management and Operations. Englewood Cliffs, N.J: Prentice Hall, 1980.
Lua MLA (9ú heag.)Gray, William S. Hotel and Motel Management and Operations. Prentice Hall, 1980.
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