1. Westman, A., Acta Obstet. Gynec. Scand., 5, 7 (1926).
2. Seckinger, D. L., and Snyder, F. F., Bull. Johns Hopkins Hospital, 39, 371 (1926).
3. Breipohl, W., Z. Gerburtshilfe Gynäk., 118, 1 (1938).
4. Borell, N., Nilsson, O., and Westman, A., Acta Obstet. Gynec. Scand., 36, 22 (1957).