1. Baer-Berlin KM. Über den Mädchenhandel. Zeitschrift für Sexualwissenschaft. 1908;9:513–28.
2. N.O. Body (Karl Baer); translation by Deborah Simon; University of Pennsylvania Press; 2005.
3. Web Reference: (Hirschfeld Institute, Germany).
http://www.hirschfeld.in-berlin.de/institut/en/personen/pers_34.html
4. Personal communication, Douglas Ousterhout, San Francisco; 2015.
5. Ousterhout DK. Feminization of the forehead: contour changing to improve female aesthetics. Plast Reconstr Surg. 1987;79:701–13.