1. Minor, P.D. et al. J. gen. Virol. 67, 1283–1291 (1986).
2. Burke, K.L., Dunn, G., Ferguson, M., Minor, P.D. & Almond, J.W. Nature 332, 81–82 (1988).
3. WHO Collaborative Study. J. biol. Stand. 9, 163–184 (1981).
4. Westrop, G.D. et al. in The Molecular Biology of Positive Strand Viruses (eds Rowlands, D.J., Mahy, B.W.J. & Mayo, M.) (Academic, London, 1986).
5. Omata, T. et al. J. Virol. 58, 348–358 (1986).