By Karlee Weinmann (April 22, 2013, 1:42 PM EDT) -- Koch Industries Inc., the conglomerate run by the billionaire Koch brothers, is firming up its interest in taking over Tribune Co.'s newspapers, a cache that includes such publications as the Los Angeles Times and the Chicago Tribune, sources told The Wall Street Journal on Sunday. Rumors swirled earlier this spring over the brothers' interest in the company, which emerged from Chapter 11 proceedings late last year and has since hired Evercore Partners and JPMorgan Chase & Co. to help a sale process. The Tribune papers, long a mainstay in the American media game, have also seen interest from greeting-card mogul Aaron Kushner, the owner of the Orange County Register and a group of other local dailies. A sale of the Tribune papers is expected to be one of the largest-ever for the newspaper industry, based on circulation. Suitors will receive financial data next month....