Greek Prime Minister George Papandreou called on Sunday for a fall referendum on "changes to the political system," including to the country's constitution. Opening a three-day parliamentary debate that will culminate in a confidence vote late Tuesday, Papandreou blamed Greece's bloated and inefficient state sector for bringing the country to its knees and vowed to effect deep changes. He also said the constitutional revision will make it easier to prosecute delinquent government officials.