Various is the correct author for any book with multiple unknown authors, and is acceptable for books with multiple known authors, especially if not all are known or the list is very long (over 50).
If an editor is known, however, Various is not necessary. List the name of the editor as the primary author (with role "editor"). Contributing authors' names follow it.
Note: WorldCat is an excellent resource for finding author information and contents of anthologies.
I've read this cover to cover. OK, not really, but it's a fantastic reference book, and I've found myself using it often since buying a copy while in college. The copious use of example sentences within the definitions along with the inclusion of short foreign-language dictionaries set it apart. Please note, however, that this thing weighs about as much as a four-year-old child. Remember to lift with the knees.