Julius Krohn and his son Kaarle set forth the historical-geographic method of comparative folk-tale research, known as the Finnish method, in The Folklore Work Method (1926). This approach involves listing literary texts of a single folk-tale chronologically and plotting the oral texts geographically. Variations are then reduced to outlines of important elements, and each element is examined for variations and patterns of distribution, finally allowing for a hypothetical "archetype" or original version. This extremely influencial method laid the basis for Stith Thompson's Motif-Index of Folk-Literature (1932--36), a huge catalog of folk-narrative elements.