Federation, Confederation, country or territory or in any other manner whatsoever", and "relinquishment of control over the Singapore Police Force or the Singapore Armed Forces", unless this has been supported at a national referendum by not less than two-thirds of the total number of votes cast. Article 6 itself and other provisions in Part III cannot be amended unless a similar procedure is followed. The requirement for a national referendum also applies to Articles 5(2A) and 5A of the Constitution, though these provisions are not yet operational. Article 5(2A) states that unless the President, acting in his personal discretion, gives a contrary written direction to the Speaker, a bill seeking to amend certain key provisions in the Constitution requires the approval of at least two-thirds of the votes cast at a national referendum. Such amendments have been called core constitutional amendments. These key provisions are the fundamental liberties in Part IV of the Constitution; provisions in Chapter 1 of Part V which deal with the President's election, powers, maintenance, immunity from suit, and removal from office; Article 93A which gives the Chief Justice or a Supreme Court judge nominated by him jurisdiction to determine whether a presidential election is valid; Articles 65 and 66 which, among other things, fix the maximum duration of Parliament at five years from the date of its first sitting, and require a general election to be held within three months after a dissolution of Parliament; any provision authorizing the President to act in his personal discretion; and Articles 5(2A) and 5A themselves. Article 5A was introduced to deal with non-core constitutional amendments. The Article enables the President to veto proposed constitutional amendments that directly or indirectly circumvent or curtail the discretionary powers conferred on him by the Constitution. However, the power to veto is not absolute as the President may, acting on the Cabinet's advice, refer the matter to a constitutional tribunal under Article 100 for its opinion on whether a proposed amendment indeed has this effect. If the tribunal's view is different from the President's, the President is deemed to have assented to the bill on the day immediately following the day when the Tribunal pronounces its opinion in open court. However, if the tribunal upholds the President's view, the Prime Minister may refer the bill to a national referendum. The President's veto is overruled if not less than two-thirds of the total number