1. Almeida, J. D., D. M. Berry, C. H. Cunningham, D. Hamre, M. S. Hofstad, L. Mallucci, K. McIntosh, andD. A. J. Tyrrell: Coronaviruses. Nature (Lond.)220, 650 (1968).
2. Anon. (1963). Methods for the Examination of Poultry Biologics (2nd ed.), Publication 1938, National Academy of Sciences ? National Research Council (Washington), pp. 60?66.
3. Apostolov, K., T. H. Flewett, andA. P. Kendall: Morphology of influenza A, B, C, and infectious bronchitis virus (IBV) virions. In: ?The Biology of Large RNA Viruses? (R. D. Barry andB. W. J. Mahy, eds.), pp. 3?26. London: Academic Press, 1970.
4. Bancroft, J. B., E. Heibert, M. W. Rees, andR. Markham: Properties of cowpea chlorotic mottle virus, its protein and nucleic acid. Virology34, 224?239 (1968).
5. Barry, R. D., P. A. Bromley, andP. Davies: The characterization of influenza virus RNA. In: ?The biology of large RNA viruses? (R. D. Barry andB. W. J. Mahy, eds.) pp. 279?300. London: Academic Press, 1970.