TY - CPAPER AU - Opriessnig T, Yu S, Thacker EL, et al TI - Derivation of porcine circovirus type 2-negative pigs from positive breeding herds T2 - Journal of Swine Health and Production DP - American Association of Swine Veterinarians DB - AASV Swine Information Library UR - https://www.aasv.org/library/swineinfo/ PY - 2004 DA - 2004/01/01 L1 - https://www.aasv.org/library/swineinfo/Content/SHAP/2004/v12n4p186.pdf ER -