Nilsson B. O., Knoth M., and Nathan E. ā€œScanning Electron Microscopy of the Responses of Postmenopausal Endometrium to Treatment With Estriol and Estriolprogesteroneā€. Upsala Journal of Medical Sciences, vol. 85, no. 1, Mar. 1980, pp. 1-6, doi:10.3109/03009738009179166.