Upon the written application of 10 percent of the registered voters in any city, presented to the city clerk prior to the municipal election, the city clerk shall insert on the ballot to be used at said election the following question: “Shall fluoride be used in the public water system?” Beside this question shall be printed the word “yes” and the word “no” with the proper boxes for the voter to indicate his or her choice. If a majority of those voting in a water system that serves one municipality at said election does not approve the use of fluoride in the public water system for said city, no fluoride shall be introduced into the public water system. If fluoride has, prior to said vote, been so introduced, such use shall be discontinued until such time as the majority of those voting in the town approve the use of such fluoride. After such popular referendum, the city clerk shall not insert the aforementioned question relative to the use of fluoride in the public water system on the ballot to be used at the municipal election for a minimum period of 3 years from the date of the last popular referendum, and only upon written application at that time of not less than 10 percent of the registered voters of said city. The procedure for a referendum on the use of fluoride in a city that is part of a water system serving more than one municipality shall be the procedure in N.H. Rev. Stat. § 485:14-a.