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