Birds and viruses at a crossroad--surveillance of influenza A virus in Portuguese waterfowl. oleh Conny Tolf, Daniel Bengtsson, David Rodrigues, Neus Latorre-Margalef, Michelle Wille, Maria Ester Figueiredo, Monika Jankowska-Hjortaas, Anna Germundsson, Pierre-Yves Duby, Camille Lebarbenchon, Michel Gauthier-Clerc, Björn Olsen, Jonas Waldenström