Petitions for including additional territory within an existing district may be filed with the Council, and the proceedings herein provided for in the case of petitions to organize a district shall be observed in the case of petitions for such inclusion. The Council shall prescribe the form for such petition. In referendum upon petitions for such inclusion, all owners of land lying within the proposed additional area shall be eligible to vote. (Amended 1959, No. 329 (Adj. Sess.), § 11(c), eff. March 1, 1961.)