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
Poulos C, Riewpaiboon A, Stewart JF, Clemens J, Guh S, Agtini M, Anh DD, Baiqing D, Bhutta Z, Sur D, Whittington D. Cost of illness due to typhoid fever in five Asian countries. Trop Med Int Health. 2011 Mar 1;16(3):314-23.
Rothman KJ, Glass RL, Espinal F, Velez H. Caries-free teeth in the absence of fluoride ion. J Public Health Dent. 1972;32(4):225-8. doi: 10.1111/j.1752-7325.1972.tb03977.x