Providing for the submission to the qualified electors of the City of Philadelphia of an amendment to Article VIII, Chapter 5 of the Philadelphia Home Rule Charter, entitled "Referenda Approved by the Voters," by adding a new section calling on the citizens of Philadelphia to urge the Philadelphia Board of Revision of Taxes (BRT) to retain its current method of real estate tax assessment and not change the method as proposed under the BRT's Full Valuation Initiative; fixing the date of a special election for such purpose; prescribing the form of ballot questions to be voted on; and authorizing — Open Common Ground