"We say that all options are there and must be put on the table, " said Abdul Basit Sieda, the group's leader.

CNN: STORY HIGHLIGHTS

But Abdul Basit Tariq, the imam, says the row died down a bit after the mosque opened in October, with the mayor of Berlin present.

ECONOMIST: Muslims and city politics

The study by Grant Graziani, Wilbert van der Klaauw, and Basit Zafar of the New York Fed staff was based on two surveys of about 200 workers.

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