- Weis, Frederick Lewis, and Walter Lee Sheppard. The Magna Charta sureties, 1215: the barons named in the Magna Charta, 1215 and some of their descendants who settled in America. (Baltimore [Maryland]: Genealogical Pub. Co., Unknown edition (1955-1999)).
- The Ancestry of Ensign Constant and Captain Thomas Southworth, p. 32.
- The source database shows Rosamond and Thomas m. 1563 and further shows they had eleven children. Weis gives a marriage date of 1563/1571.
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