This history begins with the Oxford English Dictionary (OED), which was 70 years in the making and aimed at "...exhibiting the history and significance of English words now in use, or known to have been in use since the middle of the 12th century".[5] William Craigie, one of the editors of the OED, tutored undergraduates at Oxford including Tolkien, who he later invited to work as a junior editor of the OED. According to Daniel Grotta-Kurska,[6] Tolkien’s biographer, it was Craigie who provided "Tolkien’s greatest impetus to transform Elvish from an experiment to a life-long pursuit".[7]