Kelly's study of the rise, development, and use of formularies during the foundational eras of the church is the standard work on the subject. He examines New Testament doctrinal elements; explores the relation of creeds to baptismal rites; and compares Roman, Eastern, and Western catechisms to those (familiar and obscure) propounded by 4th-century councils. Kelly completed this extensive revision of Early Christian Creeds creating the third edition in 1971. Using this in addition to A. M. Ritter's Das Konzil von Konstantinopel und sein Symbol: Studien zur Geschichte und Theologie des II. Vkumenischen Konzils, published in 1965, scholars can amass a complete bibliography of works in this area of study published prior to 1971.