Het volkomen huwelijk. Een studie omtrent zijn physiologie en zijn techniek: voor den arts en den echtgenoot geschreven.

English translation: Ideal Marriage: Its Physiology and Technique. (1930). The first printing had an insert: "The sale of this book is strictly limited to members of the medical profession, Psychoanalysts, Scholars, and to such adults as may have a definite position in the field of Physiological, Psychological, or Social Research." In its different editions and translations over the nearly 100 years since it was published, it is possible that this work sold more copies than virtually any other book in this bibliography.