Territory not within the boundaries of the City may be annexed to and become a part of the City of Greenwood Village, as provided by the statutes of the State of Colorado. No ordinance annexing lands used or zoned for residential purposes shall become effective unless such ordinance is first referred by the Council to the registered electors of the City and said ordinance is approved by a majority of the electors voting on said ordinance at the next regular election or at a special election called for such purpose. If a special election is called for such purpose, the election shall be conducted by mail ballot election, in accordance with the applicable provisions of Colorado Law. (Amended at election held Nov. 7, 1995: amended at election held Nov. 6, 1990)