Dunne, H. W., Wang, J. T. and Ammerman, E. H.1971. Classification of North American porcine enteroviruses: a comparison with European and Japanese strains. Infect. Immun.4: 619-631.
Harding, J. D. J., Done, J. T. and Kershaw, G. F.1957. A transmissible polioencephalomyelitis of pigs (Talfan Disease). Vet. Rec.69: 824-832.