BAGHDAD (AP) — The Islamic State rakes in up to $50 million a month from selling crude from oilfields under its control in Iraq and Syria, part of a well-run industry that U.S. diplomacy and airstrikes have so far failed to shut down, according to Iraqi intelligence and U.S. officials. Oil sales — the extremists' largest single source of continual income — are a key reason they have been able to maintain their rule over their self-declared "caliphate" stretching across large parts of Syria and Iraq.Read more on NewsOK.com