Oral literature and popular tradition preserved among a people. It may take the form of fairy tales, ballads, epics, proverbs, and riddles. Studies of folklore began in the early 19th century and first focused on rural folk and others believed to be untouched by modern ways. Several aims can be identified. One was to trace archaic customs and beliefs. In Germany Jacob and Wilhelm Grimm published their classic collection of fairy tales in 1812. James George Frazer's The Golden Bough (1890) reflects the use of folklore as a tool to reconstruct ancient beliefs and rituals. Another motive for the study of folklore was nationalism, which reinforced ethnic identity and figured in struggles for political independence. The catalog of motifs of folktales and myths developed by Antti Aarne and Stith Thompson encouraged comparisons of variants of the same tale or other item from different regions and times. In the mid-20th century, new trends emerged. Any group that expressed its inner cohesion by maintaining shared traditions qualified as a folk, whether the linking factor be occupation, language, place of residence, age, religion, or ethnic origin. Emphasis also shifted from the past to the present, from the search for origins to the investigation of present meaning and function. Change and adaptation within tradition were no longer necessarily regarded as corruptive.