1. Universidad Popular Autonoma del Estado de Puebla, Puebla, PUE, Mexico
2. Dorrington Medical Associates, Houston, TX, USA
3. Universidad Autonoma de Baja California, Houston, TX, USA
4. University of North Texas, Denton, TX, USA
5. The University of Texas Health Science Center at Houston, Houston, TX, USA
6. The University of Texas Medical Branch at Galveston, Galveston, TX, USA
7. United Memorial Medical Center, Houston, TX, USA
8. Division of Pulmonary, Critical Care & Sleep Medicine, Health Science Center, Texas A&M University, Corpus Christi, TX, USA