Genealogy of the Families of the Presidents, Reginald Buchanan Henry, 1935.[A historical tidbit here: There are several recognized genealogical
numbering systems (of which the Parke Society is one). Reginald Henry created what has come to be known as the Henry System, which uses a series of digits to describe the place of the descendant in the family scheme. It can get rather complex as the generations go, and once you move beyond the
9th child you run into the possibility of confusion. If you see in a compiled genealogy something like: 138523, you are looking at a Henry Number.]Not Represented)