Whenever an election is to be held under the provisions of this Plan, notice thereof shall be given by advertisement published once a week for three consecutive weeks in one or more newspapers of general circulation in the District, the first publication in each instance to be made at least twenty-one days prior to the date of the election and the last publication in each instance to be made not more than seven days prior to the date of the election. Such notice shall state the time, place, and purpose of the election. Such election shall be held and conducted and the returns thereof made, examined, and cast up in the same manner and in all respects as provided by law for the election of state and county officers. All registered voters residing in said District, subdistrict, or other area in which an election is to be held shall be entitled to vote at such election.