Leonard Riggio, founder and chairman of Barnes & Noble (NYSE: BKS), has expressed interest in acquiring the company’s retail business and spinning out its Nook tablet unit.www.barnesandnobleinc.com

The Knight Capital Group (NYSE: KCG) plans to sell its credit-brokerage group to Stifel Financial Corp. (NYSE: SF), according to Bloomberg. Knight Capital recently agreed to be acquired by Getco.www.knight.com

Opera Software (OSLO: OPERA) announced that it will spin off its advertising business into a wholly-owned subsidiary called Opera Mediaworks. www.opera.com

Sinopec of China has agreed to acquire half of Chesapeake Energy Corp.‘s (NYSE: CHK) Mississippi Lime oil and gas properties for $1.02 billion. www.chk.com

Doughty Hanson is preparing a public float for HellermannTyton, a global maker of fastening, routing and identification products, according to Sky News. Goldman Sachs and JPMorgan would serve as lead underwriters, while London seems to be the most likely listing location. www.hellermanntyton.com

Palladium Equity Partners is seeking a buyer for Cannella Response Television, a Burlington, Wis.-based direct response media agency, according to peHUB. Also selling would be minority shareholder ZM Capital. http://www.drtv.com

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