Hankscraft Inc. Patent application title: Traffic Light Heater. Class name: Heating devices combined with diverse-type art device electrical devices, 20120255942. United States Patent Office. 11 October 2012 [11 October 2012]. (原始内容存档于2015-06-29).
"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.
Hankscraft Inc. Patent application title: Traffic Light Heater. Class name: Heating devices combined with diverse-type art device electrical devices, 20120255942. United States Patent Office. 11 October 2012 [11 October 2012]. (原始内容存档于2015-06-29).