Allen, J. E. (1915). On the electrification of freight yards: An investigation upon the construction and operation and the effect upon the city plan of the proposed Overbrook Classification Yard of the Pennsylvania Railroad. Philadelphia: Dept. of Public Works.

Allen, John E. On the Electrification of Freight Yards: An Investigation Upon the Construction and Operation and the Effect Upon the City Plan of the Proposed Overbrook Classification Yard of the Pennsylvania Railroad. Philadelphia: Dept. of Public Works, 1915.

Allen, John E. On the Electrification of Freight Yards: An Investigation Upon the Construction and Operation and the Effect Upon the City Plan of the Proposed Overbrook Classification Yard of the Pennsylvania Railroad. Philadelphia: Dept. of Public Works, 1915.