The Triennial Act of 1641 reference article from the English Wikipedia on 24-Apr-2004
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Triennial Act of 1641

The Triennial Act, of 1641, was a piece of legislation passed by the English Long Parliament, during the reign of King Charles I. The act requires that the Parliament meet for at least a fifty-day session once every three years. It was intended to prevent Kings from ruling without Parliament, as had been done between 1629 and 1640. In 1664, it was repealed.