Stratz, op. cit., Chapter XII.
W. S. A. Griffith, "The Diagnosis of Pregnancy," British Medical Journal, April 11, 1903.
J. Mackenzie and H. O. Nicholson, "The Heart in Pregnancy," British Medical Journal, October 8, 1904; Stengel and Stanton, "The Condition of the Heart in Pregnancy," Medical Record, May 10, 1902 and University Pennsylvania Medical Bulletin, Sept., 1904 (summarized in British Medical Journal, August 16, 1902, and Sept. 23, 1905.)