Federal Air Travel Restrictions for Public Health Purposes -- United States, June 2007-May 2008. - Penfield, S.; Flood, J.; Lang, W.; Zanker, M.; Alvarado-Ramy, F.; Leidel, L.; Fowler, G.; Modi, S.; Brown, C.; Averhoff, F.; Haddad, M. B. (MMWR: Morbidity & Mortality Weekly Report, 2008)