The Aarne–Thompson–Uther Index is a catalogue of folktale types used in folklore studies. The ATU index is the product of a series of revisions and expansions by an international group of scholars: Originally published in German by Finnish folklorist Antti Aarne (1910), the index was translated into English, revised, and expanded by American folklorist Stith Thompson, and later further revised and expanded by German folklorist Hans-Jörg Uther (2004). The ATU index is an essential tool for folklorists, used along with the Thompson (1932) Motif-Index of Folk-Literature.