4Pol JMA, Wagenaar F, Reus JEG. Comparative morpho- genesis of three PRRS virus strains ~J3. Veterinary Microbiology, 1997,55(1-4) : 203-208.
5S. Joo, B. K. Park, S. A. Dee and C. Pijoan. Indirect fluorescent Ig M antibody response of pigs infected with porcine reproductive and respiratory syndrome virus [J]. Veterinary Mi- crobiology 1997,55(1-4):303-307.
6K. J. Srensen , A. Btner, Smedegaard , et al . Evalufion of a blocking Elisa for screening of antibodies against porcine re- productive and respirtory syndrome (PRRS) virus (JJ. Veterinary Microbiology, 1996,56(1-2):1-8.
7K. J. Srensen , B .Strandbyan , A. Btner, et al . Block- ing ELISA's for the distinction between antibodies against Euro- pean and American strains of porcine ~eproductive and respiratory syndrome virus [J]. Veterinary Microbiology, 1998,60(2-4): 169- 177.
8Jusa ER, Inaba Y, Kouno M, et al. Slow-reacting and complement requiring neutralizing antibody in swine infected with porcine reproductive and respiratory syndrome (PRRS) virus [J}. J Vet Med Sci, 1996,58:749-753.
9Botner A, Nielsen J, BiUe-Hansen V. Isolation of porcine reproductive and rrespirtory syndrome (PRRS) virus in a Danish swine herd and experimental infection of pregnant gilts with the virus[J]. Veterinary Microbiology, 1994,40(3-4): 351~360.