It has been said many times before, and it will be many times again: Warren Buffett is the greatest investor of all time. Among the many world-class businesses in Berkshire Hathaway's $345.4 billion investment portfolio, here are two that I think dividend growth investors should strongly consider buying this month. It's no secret that Buffett and his business partner Charlie Munger prefer to invest in businesses that are profitable and possess competitive moats.