Section 129. At the regular municipal election to be held in the year nineteen hundred and seventy-seven in every city there shall be placed upon the ballot the two following questions:—

''A BINDING REFERENDUM CHANGING THE STRUCTURE OF THE CITY COUNCIL TO PROVIDE FOR DISTRICT REPRESENTATION.

''A BINDING REFERENDUM CHANGING THE STRUCTURE OF THE SCHOOL COMMITTEE TO PROVIDE FOR DISTRICT REPRESENTATION.

In subsequent years, either or both of the above questions shall be placed upon the ballot of a regular municipal election in any city by a petition addressed to the city council of such city, signed by qualified voters of the city in a number equal at least to five per cent of the number of registered voters in said city at the state election next preceding the filing of said petition. Such petition shall be filed with the city clerk, who shall transmit the same forthwith to the registrars of voters or city body functioning as such, who shall within sixty days certify the signatures thereon in accordance with the provisions of law and return the same to the city clerk. The petition shall be filed with the city clerk at least one hundred and forty days before the date of the election at which the question or questions proposed by the petition is to be submitted to the voters.

Any petition submitted under this section may be in the form of separate sheets addressed to the city council, each sheet containing at the top thereof the question or questions proposed for submission to the voters. When attached together and offered for filing, the several papers shall be deemed to constitute one petition, and there shall be endorsed thereon the name and address of the person presenting the same for filing. The provisions of sections nine and ten shall apply to any petition filed hereunder, and to the placing upon the ballot of any question or questions proposed therein.