BOSTON –  Shares of pharmaceutical research services provider Covance Inc. tumbled 9% to $43.00 on Thursday, the day after it released a lackluster quarterly earnings report and said that it sees 2012 earnings per share coming in between $2.50 and $2.80. Analysts polled by Thomson Reuters had estimated the company would post earnings of $2.92 a share, on average. Covance also announced its board had authorized a share buyback program of up to $300 million.

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