PCV-2 genotype definition and nomenclature - Segales, J; Olvera, A; Grau-Roma, L; Charreyre, C; Nauwynck, H; Larsen, L; Dupont, K; McCullough, K; Ellis, J; Krakowka, S; Mankertz, A; Fredholm, M; Fossum, C; Timmusk, S; Stockhofe-Zurwieden, N; Beattie, V; Armstrong, D; Grassland, B; Baekbo, P; Allan, G (Vet Rec, 2008)