Columbia subject headings:
Asceticism--Islam.
Buddhism--Doctrines.
Buddhism--Relations--Islam.
Islam--Relations--Buddhism.
Sufism--Doctrines.
Harvard subject headings:
Asceticism--Buddhism.
Asceticism--Islam.
Buddhism--Doctrines
Sufism--Doctrines
Princeton subject headings:
Asceticism--Buddhism.
Asceticism--Islam.
Buddhism--Doctrines.
Sufism--Doctrines.