SECTION 56.
Section 19 of chapter 32B of the General Laws, as so appearing, is hereby amended by striking out, in lines 192 to 195, inclusive, the words "at either 3 or 6-year intervals from the date of transfer of subscribers to the commission, as determined by the written agreement which shall specify the withdrawal interval and withdrawal procedures." and inserting in place thereof the following words:- after an initial 3-year period from the date of transfer of subscribers to the commission, at whole-year intervals determined by the written agreement which shall specify the withdrawal interval and withdrawal procedures; provided, however, that such whole-year intervals shall not be less than 2 years in length.