Further adding credence to a potential bid is the lobby registration filing shows law firm Wachtell, Lipton, Rosen & Katz, which deals in mergers and acquisitions. The law firm is listed as an intermediary between Alibaba and the Duberstein group. The registration was received by the U.S. Senate on Dec. 23, but the filing notes the effective date as of Dec. 1. Alibaba may be realizing the value in owning all of Yahoo!'s properties, as opposed to just buying back its stake. There have also been reports of private equity firm Silver Lake Partners looking to buy a minority stake in Yahoo!, but that appears to have been quashed for now. Yahoo! shares were higher in Thursday trading, up 2.1% to $16.11. Interested in more on Yahoo!? See TheStreet Ratings' report card for this stock.