Royalty for Commoners: The complete Known Lineage of John of @ p 222, s of Thierri IV Count of Frisia & Othilde von Nordmark
The cited information was published by Genealogical Publishing Comp, Baltimore, MD, 1993 (Ref: p 222, s of Thierri IV Count of Frisia & Othilde von Nordmark) The author/originator was Roderick W. Stuart.
Source Notes
subtitled The Complete Known Lineage of John of Gaunt, son of
Edward III King of England & Queen Philippa. Reviewed in TAG,
April 1994 by Dr. David H. Kelly