McTeer, Frances (Davis) and Frederick C. Warner. "The Willis Family of Sudbury, Massachusetts", in The New England Historical and Genealogical Register. (Boston: New England Historic Genealogical Society) 114:96.
Inventory of "John Clapp, late of Sudbury, deceased" submitted by son John Clapp, assented to by "Peter Noyes, Husband to the sd decd's Daughter Elizabeth, and Joseph Willis, Husband of Thankful (which are all the decd's children)" [Middlesex Probate 4478].