If, within 30 days after the date of publication of an ordinance authorized by section 20r, a petition signed by not less than 10% of the registered electors residing within the limits of the township is filed with the township clerk requesting a referendum upon the effectiveness of the ordinance, then the ordinance does not become effective until approved by vote of a majority of the electors of the township qualified to vote and voting on the ordinance at an election. Signatures on the petition shall be verified by some person or persons under oath as the actual signatures of persons whose names are signed, and the township clerk shall have the same power to reject signatures and petitions as city clerks possess by law. The number of registered electors in the township shall be determined by the township clerk from the township registration books.