Columbia subject headings:
Harvard subject headings:
Shīʻah--Doctrines
Shīʻah--Relations--Sunnites.
Sunnites--Relations--Shīʻah.
Princeton subject headings:
Islam--Doctrines.
Shīʻah--Doctrines.
Shīʻah--Relations--Sunnites.
Sunnites--Relations--Shīʻah.