McLean, Va. - Attempting to boost their sagging ad revenue, four of the nation's largest newspaper publishers -- including Gannett (NYSE: GCI), Tribune (NYSE: TXA), Hearst and The New York Times Co. (NYSE: NYT) -- said on Friday that they will team to launch their own online ad sales network. The network, called quadrantONE, will work in a similar fashion to a networks launched last year by Yahoo and a group of newspapers, allowing national advertisers to buy space on more than 120 newspaper websites.