1. Heart;Abbott, M.I.;J,1928
2. intern;Blackford, L.M.;Med,1928
3. Eppinger, L. (1887). Arch. Klin. Chir. 35, 1. Fletcher. T. B. (1842). Med.-chir. Trans., 25, 282.
4. Forbus, W. D. (1930). Johns Hopk. Hosp. Bull.. 47, 239.
5. Fray. W. (1930). Amer. J. Roentgenol., 24, 349.