Piccadilly Line

1. Jobling, D. G. / Lyons, A. C. (1976): Extension of the Piccadilly Line from Hounslow West to Heathrow Central. In: Proceedings of the Institution of Civil Engineers, v. 60, n. 2 (May 1976), pp. 191-218.

   https://doi.org/10.1680/iicep.1976.3460

2. Sabine, G. D. / Skelton, E. (1985): Extension of the Piccadilly Line to Terminal 4, Heathrow. In: Proceedings of the Institution of Civil Engineers, v. 78, n. 6 (December 1985), pp. 1261-1278.

   https://doi.org/10.1680/iicep.1985.1055