Books can be attributed to "Unknown" when the author or editor (as applicable) is not known and cannot be discovered. If at all possible, list at least one actual author or editor for a book instead of using "Unknown".
Books whose authorship is purposefully withheld should be attributed instead to Anonymous.
If you've read any fantasy novel, you've read Beowulf, because of course this is one of the main traditions that fantasy writing draws on. One thing this poem is that contemporary fantasy writing obviously isn't, is a metrical, oral piece, and while this translation grammatically indicates how the meter would have been structured in the original, it does not otherwise preserve any of the metrical or lyric qualities that might have made the original work interesting.