Gray, G. E., & Hoel, L. A. (1979). Public transportation: Planning, operations, and management. Prentice-Hall.
Lua i Stíl Chicago (17ú heag.)Gray, George E., agus Lester A. Hoel. Public Transportation: Planning, Operations, and Management. Englewood Cliffs, N.J: Prentice-Hall, 1979.
Lua MLA (9ú heag.)Gray, George E., agus Lester A. Hoel. Public Transportation: Planning, Operations, and Management. Prentice-Hall, 1979.
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