Designed to accompany the standard textbook "A Basic English Grammar", this exercise book has been revised and updated to include 60 additional exercises. All exercises are cross-referenced to the textbook.
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.