1. Armstrong, J. B., and White, J. C. (1950). Lancet, 2, 739.
2. Burkhardt, R. (1965). Seminars Hemat., 2, 29.
3. Epstein, W. V., and Tan, M. (1964). Arthr. and Rheum., 7, 733.
4. Godman, G. C., Deitch, A. D., and Klemperer, P. (1958). Amer. J. Path., 34, 1.
5. Grishman, E., Porush, J. G., Rosen, S. M., and Churg, J. (1966). In Sixth International Congress for Electron Microscopy, Kyoto, edited by R. Ueda, p. 747. Maruzen Co. Ltd, Tokyo.