Columbia subject headings:
Church history--Primitive and early church, ca. 30-600--Congresses.
Clement I, Pope--Congresses.
Harvard subject headings:
Church history--Primitive and early church, ca. 30-600--Congresses.
Clement I, Pope--Congresses.
Princeton subject headings:
Church history--Primitive and early church, ca. 30-600--Congresses.
Clement I, Pope--Congresses.