Columbia subject headings:
Authors, Italian--To 1500--Correspondence.
Guittone, d'Arezzo, -1294--Correspondence.
Harvard subject headings:
Authors, Italian--To 1500--Correspondence
Guittone, d'Arezzo, -1294. Correspondence.
Princeton subject headings:
Authors, Italian--To 1500--Correspondence.
Guittone, d'Arezzo, -1294. Correspondence.