At the next general election following such special election, in the event the landowners vote in favor of an increase in the membership of the board of directors, there shall be elected two directors-at-large, one to serve for two years and one for three years, and, at each regular election thereafter held in said district immediately preceding the expiration of the term of office of any such director-at-large, a successor shall be elected to succeed him for a term of three years.L. 45: p. 420, § 6. CSA: C. 90, § 487(6). CRS 53: § 149-3-9. C.R.S. 1963: § 150-3-9.