The people reserve the power to approve or reject at the polls any legislation enacted by the City Council which is subject to the initiative process under this Charter, except that ordinances authorizing the issuance of either tax or revenue bonds, whether original or refunding bonds, shall not be subject to such referendum. Prior to or within thirty (30) days after the effective date of any ordinance which is subject to referendum, a petition signed by qualified voters of the City equal in number to at least twenty percent (20%) of the qualified voters of the City may be filed with the City Secretary requesting that any such ordinance be either repealed or submitted to a vote of the people. When such a petition has been certified as sufficient by the City Secretary, the ordinance specified in the petition shall not go into effect, or further action thereon shall be suspended if it shall have gone into effect, until and unless it is approved by the voters as herein provided.