Efficacy of an American and a European serotype PRRSV vaccine after challenge with American and European wild–type strains of the virus G.G. Labarque, H.J. Nauwynck, P.A.M. van Woensel, N. Visser and M.B. Pensaert Vet. Res., 31 1 (2000) 97 DOI: 10.1051/vetres:2000026