The Adventures of Tom Bombadil, Christina Scull 
The J. R. R. Tolkien Companion and Guide: Volume 1: Chronology, Christina Scull 
The J. R. R. Tolkien Companion and Guide: Volume 2: Reader’s Guide PART 1, Christina Scull 
The J. R. R. Tolkien Companion and Guide: Volume 3: Reader’s Guide PART 2, Christina Scull