March, Charles E. (August 1934). "The Local Transportation Problem in the District of Columbia". The Journal of Land and Public Utilities Economics. 10 (3). University of Wisconsin Press: 275–290. doi:10.2307/3139173. JSTOR3139173.
March, Charles E. (August 1934). "The Local Transportation Problem in the District of Columbia". The Journal of Land and Public Utilities Economics. 10 (3). University of Wisconsin Press: 275–290. doi:10.2307/3139173. JSTOR3139173.