Any municipality which has heretofore enacted a regulation or public record by reference thereto shall not be required to re-enact such regulation or public record by reason of this Division 3, and all previous incorporations by reference which would have been valid if this Division 3 had then been in effect, are hereby ratified and declared effective, provided, however, that the requisite number of copies are forthwith filed with the clerk of such municipality, if they have not already been so filed.