After Tolkien's death, his son Christopher published a series of works based on his father's extensive notes and unpublished manuscripts, including The Silmarillion. These, together with The Hobbit and The Lord of the Rings, form a connected body of tales, poems, fictional histories, invented languages, and literary essays about a fantasy world called Arda and Middle-earth within it. Between 1951 and 1955, Tolkien applied the term legendarium to the larger part of these writings.