Elton, J. (1988). Engineering and engineers, bridges, rives and canals, railways and the esteam engine, electric telegraph (1ª ed.). London: Elton Engineering Books.
Cita MLA (8 ed.) (Copiar al portapapeles)Elton, Julia. Engineering and Engineers, Bridges, Rives and Canals, Railways and the Esteam Engine, Electric Telegraph. 1ª ed. London: Elton Engineering Books , 1988.