Conversation so far:
Why is the Islamic constitution important to Khomeini?
the Shah announced the "White Revolution", a six-point programme of reform.
What happened next?
Ayatollah Khomeini summoned a meeting of the other senior marjas of Qom and persuaded them to decree a boycott of the referendum on the White Revolution.

Question: What year did this happen?
Self-contained rewrite: What year did Ayatollah Khomeini summon a meeting of the other senior marjas of Qom and persuade them to decree a boycott of the referendum on the White Revolution?