Franklin JM, Dejene S, Huybrechts KF, Wang SV, Kulldorff M, Rothman KJ. A bias in the evaluation of bias comparing randomized trials with nonexperimental studies. Epidemiol Methods. 2017 Apr;6(1):20160018.. doi: 10.1515/em-2016-0018.
Brodtkorb T, Kogler GF, Arndt A. The influence of metatarsal support height and longitudinal axis position on plantar foot loading. Clin Biomech (Bristol, Avon). 2008;23(5):640-7.