The Motif-Index of Folk-Literature is a six volume catalogue of motifs, granular elements of folklore, composed by American folklorist Stith Thompson (1932-1936, revised and expanded 1955-1958). Often referred to as Thompson's motif-index, the catalogue has historically received extensive use in folklore studies, where folklorists commonly use it in tandem with the Aarne–Thompson–Uther Index, an index used for folktale type analysis.
Stith Thompson (March 7, 1885 – January 13, 1976) was an American scholar of folklore. He is the "Thompson" of the Aarne-Thompson classification system, which indexes certain folktales by their structure and assigns them AT numbers. He also developed an alpha-decimal motif-index system (A~Z followed by numeral) for cataloging individual motifs.
It is very interesting to see how ubiquitous some of the myths are throughout the varied cultures of the world. This was one of the sources used in Funk and Wagnall's Standard Dictionary of Folklore, Mythology, and Legend, which I read last summer, I believe.
Broken down into a lot of sections and sub-sections so the reader/researcher can see how the smaller motifs share a common thread with larger, more common ones.