An initiatory or a referendary petition shall be signed by registered electors of the city equal to not less than fifteen percent of the number of registered electors of the city according to the records of the Clerk on the date of the last previous regular city election. No referendum shall be permitted respecting any ordinance required to be passed by the Council by any law, except in the manner provided by such law. Such petition may be the aggregate of two or more petition papers. Each signer of a petition shall sign his name and shall, himself, place thereon after his name, the date and his place of residence by street and number. To each petition paper there shall be attached a sworn affidavit by the circulator thereof, stating that each signature thereon is the genuine signature of the person whose name it purports to be and that it was signed in the presence of the affiant. Such petition shall be filed with the Clerk who shall, within ten days, canvass the signatures thereon to determine the sufficiency thereof. Any signatures obtained more than sixty days before the filing of such petition with the Clerk shall not be counted. If found to contain an insufficient number of signatures of registered electors, or to be improper as to form or compliance with the requirements of this section, the Clerk shall notify, forthwith, the person filing such petition, and ten days from such notification shall be allowed for the filing of supplemental petition papers. When found sufficient and proper, the Clerk shall present the petition to the Council at its next regular meeting.