Attrition of advanced trauma life support (ATLS) skills among ATLS instructors and providers in Mexico - Azcona, Luis A.m; Gutierrez, Guillermo E.O.; Fernandez, Cesar J.P.; Natera, Octavio M.; Speare, Octavio Ruiz-; Ali, Jameel; Azcona, Luis Am; Ruiz-Speare, Octavio (Journal of the American College of Surgeons, 2002)