Weeds are the most serious biological constraint to upland rice production.

"These are all people who have serious constraints on their time," he said.

St. Luke's infant years were a period of healthy congregational growth, but compounded with serious financial constraints.

That had put a serious constraint on his mobility.

Mr. Yeltsin, the dominant opposition figure, operates with serious constraints.

A waiver program is in place for families with serious financial constraints.

I must emphasise, however, that there are serious constraints.

Previously, financial market worries have been a serious constraint on governments.

It got a grab-bag bill that imposes serious constraints on the expansion of commercial banks.

That is a serious constraint, but Congress is not about to rewrite the law.