Columbia subject headings:
Chrétien, de Troyes, active 12th century--Influence.
Guillaume, le Clerc, active 13th century. Fergus.
Harvard subject headings:
Chrétien, de Troyes, active 12th century--Influence--Guillaume le Clerc.
Guillaume, le Clerc, active 13th century. Fergus.
Princeton subject headings:
Chrétien, de Troyes, active 12th century--Influence--Guillaume le Clerc.
Guillaume, le Clerc, active 13th century. Fergus.