Columbia subject headings:
Harvard subject headings:
Islam--History
Schism--History.
Shiites--History
Sunnites--History.
Sunnites--Relations--Shīʻah
Princeton subject headings:
Ethnic conflict--Middle East--21st century.
Ethnic conflict--Religious aspects--Islam.
Islam and politics.
Shiites--Middle East--21st century.
Shīʻah--Relations--Sunnites--21st century.
Sunnites--Middle East--21st century.
Sunnites--Relations--Shīʻah--21st century.