1. Berblinger, W. (1915). Virchows Arch. path. Anat., 219, 328.
2. Bjorneboe, M. (1934). Frankfurt Z. Path., 47, 363.
3. Fowler, M., and Simpson, D. A. (1962). J. Path. Bact., 84, 307.
4. Gibson, J. B., Burrows, D., and Weir, W. P. (1957). Ibid., 74, 419.
5. Grahl, F. (1906). Beitr. path. Anat., 39, 66.