Columbia subject headings:
Abbots--France--Correspondence.
Authors, Latin (Medieval and modern)--Correspondence.
France--History--Charles II, 840-877--Sources.
Lupus, of Ferrières, approximately 805-approximately 862--Correspondence.
Harvard subject headings:
France--History--Charles II, 840-877--Sources.
Lupus, of Ferrières, approximately 805-approximately 862. Correspondence
Princeton subject headings:
Lupus, of Ferrières, 800-863--Correspondence.