Brian Haresnape
Hardy, Brian
Glover, John
Asociación de Investigación del Transporte (Spain)
N. J. van Wijck Jurriaanse
David Larkin
Unknown Author
United States. Congress. Senate. Committee on Interstate Commerce
Donald MacQueen Street
Symposium on Rapid Transit Vehicles for City Services London 1971.
František Kreisel
Österreichische Gesellschaft für Eisenbahngeschichte. Arbeitskreis Steyrtalbahn.
Gottfried Bauer
Great Britain. Inter-service Topographical Dept.
Klaus Joachim Schrader
Charles Henry Markham
World's Columbian Exposition (1893 Chicago, Ill.)
Ludvík Losos
Carl W. Schmiedeke