The signatures to a petition to initiate or refer an ordinance need not all be appended to one paper. One of the signers of each paper shall make an oath before an officer competent to administer oaths that the person believes the statements in the paper to be true and that each signature to the paper is the genuine signature of the person whose name it purports to be. Any petitioner may withdraw that petitioner’s name from a petition within five days after the date of the filing of the petition with the city auditor.