Prior to the holding of any public hearing prescribed in Section 6 of this Act, or any meeting regarding the passage of any resolution to file a law suit, the Commission shall give notice to such grantee or lessee, or his or their legal representatives, successors or assigns, of the time and place of such proceeding. Such notice shall be accompanied by a statement signed by the Secretary of the Commission, or by any person authorized by the Commission to sign the same, setting forth any act or things done or omitted to be done in violation, or claimed to be in violation, of any restriction as to the use of such property, whether such restriction be prescribed in any of the terms of this Act or by any restriction as to the use of such property determined by the Commission pursuant to the terms of this Act. Such notice of the time and place fixed for such proceeding shall also be given to such person or persons as the Commission shall deem necessary. Such notice may be given by registered mail, addressed to such grantee, lessee, or to their legal representatives, successors or assigns, at the last known address of such grantee, lessee, or their legal representatives, successors or assigns.