Prior infection with an H1N1 swine influenza virus partially protects pigs against a low pathogenic H5N1 avian influenza virus., Van Reeth, Kristien, Braeckmans Debby, Cox Eric, Van Borm Steven, van den Berg Thierry, Goddeeris Bruno, and De Vleeschauwer Annebel , Vaccine, 2009 Oct 23, Volume 27, Issue 45, p.6330-9, (2009)