Distinction between infections with European and American/vaccine type PRRS virus after vaccination with a modified-live PRRS virus vaccine A. Bøtner, B. Strandbygaard, K.J. Sørensen, M.B. Oleksiewicz and T. Storgaard Vet. Res., 31 1 (2000) 72 DOI: 10.1051/vetres:2000009