The Norwegian Folktale Index developed by Ørnulf Hodne in 1984, based on The Aarne Thompson Index (AT)

To get an overview of the diverse folktale tale tradition, several type indexes have been developed. The most well-known international index was created by Antti Aarne and Stith Thompson, and is called the AT index. It was revised and expanded by Hans-Jörg Uther in 2004, and it is now known as the ATU index.

The index uses the narrative structure as an organizing principle, the sequence of events or motifs determines a folktale type number. Such motif indexes were developed as a methodological device for research, particularly those researchers interested in tracing the migration and development of folktale motifs. Based on stories that are quite similar, that is, individual narratives considered as variants of the same tale, an ideal story, a so-called type, was abstracted.

The AT index has served as a model for several national folktale index, including the Norwegian folktale catalogue, Ørnulf Hodne's The Types of the Norwegian Folktale (1984). This national index is used by SAMLA. Therefor SAMLA refers to AT numbers, and not ATU numbers.