Hankscraft Inc. (11. oktober 2012). "Patent application title: Traffic Light Heater". Class name: Heating devices combined with diverse-type art device electrical devices, 20120255942. United States Patent Office. Hentet 11. oktober 2012.
"Westminster Street Semaphore Signals.-Gas." Times [London, England] 6 Jan. 1869: 10. The Times Digital Archive. Web. 5 Aug. 2015. Describes the explosion but does not mention the fate of the policeman.