Verlyn Flieger and Carl F. Hostetter (eds.). Tolkien's Legendarium: Essays on The History of Middle-earth(英语:Tolkien's Legendarium). Greenwood Press. 2000. ISBN 0-313-30530-7.
Michael D. C. Drout (ed.). J. R. R. Tolkien Encyclopedia. 羅德里奇. 2006. ISBN 0-415-96942-5.