Bourne JE, Sauchelli S, Perry R, Page A, Leary S, England C, Cooper AR. Health benefits of electrically-assisted cycling: a systematic review. Int J Behav Nutr Phy. 2018 Nov 21;15(1):116. doi: 10.1186/s12966-018-0751-8
Mines D, Abbuhl SB. Hydroxyapatite pseudopodagra in a young man: acute calcific periarthritis of the first metatarsophalangeal joint. Am J Emerg Med. 1996 Mar;14(2):180-2.