An advertising industry association--backed by four of the world's largest ad agencies--sent a letter to the DoJ endorsing the Microsoft-Yahoo search deal, saying it "enhances competition," and has the potential to serve as a powerful check on Google's dominance of that market. American Association of Advertising Agencies President and CEO Nancy Hill posted the open letter, which was also signed by Maurice Levy, chairman and CEO of Publicis Groupe; Martin Sorrell, CEO of WPP; Michael I. Roth, chairman and CEO of Interpublic Group of Companies; and John Wren, president and CEO of Omnicom Group. "We believe that Yahoo and Microsoft's proposal to combine their technologies and search platforms’s good for advertisers, marketing services agencies, website publishers and consumers," they said in the letter.