All meetings of public bodies, as defined hereinafter, shall be held at specified times and places which are convenient to the public and shall be open to the public, except as hereinafter specifically provided. All meetings of such public bodies, except for executive sessions of the State Banking Board and Oklahoma Savings and Loan Board, shall be preceded by advance public notice specifying the time and place of each such meeting to be convened as well as the subject matter or matters to be considered at such meeting, as hereinafter provided.