In the DSM III, published in 1980, transsexualism was to be diagnosed and the sexual orientation of a transsexual specified using the terms "homosexual", "heterosexual", "asexual", or unspecified. This convention had its origins in the taxonomic work of researchers like Hirschfeld, Benjamin, and Freund, which found that grouping trans women by sexual orientation reveals important qualitative and statistical differences between them. These differences have been maintained by various researchers as indicative or suggestive of multiple, distinct etiologies. The term "homosexual transsexual" has since been used in publications by a variety of academics, including Benjamin, Freund, Blanchard, and Anne Lawrence, as well as J. Michael Bailey and James Cantor, among others. Sexologist Ray Blanchard uses the concept in relation to one type of male-to-female (MTF) transsexual in his transsexualism typology developed in the late 1980s.