«Hail». National Center for Atmospheric Research, University Corporation for Atmospheric Research, 2008. Arxivat de l'original el 2010-05-27. [Consulta: 18 juliol 2009].
«Hail». National Center for Atmospheric Research, University Corporation for Atmospheric Research, 2008. Arxivat de l'original el 2010-05-27. [Consulta: 18 juliol 2009].