§ 5

The regulations imposed and the districts created under the provisions of this act may be changed or altered from time to time by ordinance, but no such change or alteration shall be made until the proposed change shall have been referred to the zoning commission for a hearing. Said commission shall, upon receipt from the board of aldermen of such proposed change, give notice and proceed with a hearing in the same manner as is herein provided and shall report to said board of aldermen its recommendations in the matter, within thirty days after receipt by it of the proposal for a change. Thereafter the board of aldermen may, by ordinance adopted in the usual manner, make the proposed change. When the owners of fifty per centum of the frontage in any district or part thereof shall present a petition to the mayor requesting an amendment or repeal of any such regulation, the mayor shall forthwith refer such proposed amendment or repeal to the commission for its further consideration and recommendation, and said commission shall, within ninety days from the receipt of such petition, submit a report to the board of aldermen of said city of such approval or disapproval. If twenty per centum of the owners of the frontage of the property immediately affected by the proposed amendment or repeal or, if the owners of twenty per centum of the frontage of the rest of the block or blocks affected or the owners of twenty per centum of the frontage directly opposite the property immediately affected by such amendment or repeal, shall, within fifteen days after the filing of the report of said commission, file a protest in writing, signed by them with the city clerk, such amendment or repeal shall not be adopted unless recommended by the zoning commission or unless three-fourths of the members of the board of aldermen shall vote in favor of such amendment or repeal.