With Mehta , Saberi , and Umesh Vazirani , he showed in 2007 how to formulate the problem of choosing advertisements for AdWords as an online matching problem .
With Mehta , Saberi , and Umesh Vazirani , he found a solution to this problem with optimal competitive ratio .
With Mehta , Saberi , and Umesh Vazirani , he showed in 2007 how to formulate the problem of choosing advertisements for AdWords as an online matching problem , and found a solution to this problem with optimal competitive ratio .