Concussion in American versus European professional soccer: A decade-long comparative analysis of incidence, return to play, performance, and longevity - Ramkumar, P. N.; Navarro, S. M.; Haeberle, H. S.; Luu, B. C.; Jang, A.; Frangiamore, S. J.; Farrow, L. D.; Schickendantz, M. S.; Williams, R. J. (The American Journal of Sports Medicine, 2019)