The gynecological treatises "On the Nature of the Woman", "On the Diseases of Women", "Generation", "On the Nature of the Child", and "On Sterile Women" constitute a closely related group. identified five layers of material in this group, from the mid-fifth century to the mid-fourth century. The oldest stratum is found in "On the Nature of the Woman" and "On the Diseases of Women" II. "Generation" and "On the Nature of the Child" constitute a single work by a late-fifth-century author, who may also be identified as the author of "On Diseases" IV and of sections of "On the Diseases of Women" I. The latest layer is "On Sterile Women", which was composed after the other gynecological treatises were in existence.