Going after Aron's cash would complicate matters with Riverstone, which still wields sway over the board.

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The Quadrangle settlement comes after settlements last year by Carlyle Group and Riverstone Holdings, but the investigations continue.

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Carlyle Group and Riverstone Holdings have both already gotten off with fines for defrauding the public with similar bribery scams.

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Prior to that, he served as CEO and President of Riverstone Networks, a network company focused on Metro Ethernet switching.

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