Some periodicals ("publications issued at regular, or irregular intervals") were published locally as early as the late 18th and early 19th centuries, although most useful ones for genealogical research began later. Of particular note are the often annual publications of County archaeological societies from the 1840's which contain hundreds of articles about local families and their descent and are usually well indexed. From the 1970s newly formed family history societies began publishing regular newsletters which have become more substantial.