Hedwige of Germany (Browning, Charles H. Americans of royal descent, 7th ed. Baltimore : Genealogical Pub. Co., 1986, pg. 468).

Stammtafeln says she is the daughter of Henry, Margrave of Mark (d 886).
and not Arnulf. There are only 13 years between the aproximate birth of
Arnulf and Henry the Fowler, which implies some further re checking of
sources is in order! (WWW site: Directory of royal genealogical data) - yet this site does claim her as a daughter of Arnoul (Arnulf).