1. Universidad Veracruzana, Xalapa, Mexico
2. Dorrington Medical Associates, Houston, TX, USA
3. Universidad Autonoma de Baja California, Mexicali, Mexico
4. Texas A&M University-Corpus Christi, Corpus Christi, TX, USA
5. Acute and Continuing Care, Houston, TX, USA
6. The University of Texas Health Science Center, Houston, TX, USA
7. The University of Texas Medical Branch at Galveston, Houston, TX, USA
8. United Memorial Medical Center/United General Hospital, Houston, TX, USA