A new ring is added every year, and thicker rings represent a kind of savings account, when the tree collects more nutrients than it can use.

VOA: standard.2010.04.05

With Iran now facing intensified pressure to provide a complete account of all of its enrichment and any weapons-related activities, revelation of the new enrichment facility reinforced the determination of U.S.lawmakers to move ahead with tougher sanctions.

VOA: standard.2009.09.25