The Book of Concord or Concordia is the doctrinal standard of the Lutheran Church. It is composed of ten documents, each of which has been recognized as authoritative in Lutheranism since at least the 16th century. (The Three Ecumenical Creeds, The Augsburg Confession, The Apology of the Augsburg Confession, The Smalcald Articles, A Treatise of the Power and Primacy of the Pope, Luther's Small and large Catechisms, and The Formula of Concord.) They are also known as the symbolical books of the Evangelical Lutheran Church, or the Lutheran Confessions. The Book of Concord was published in German on June 25, 1580 in Dresden; this date was chosen to commemorate the fiftieth anniversary of the presentation of the Augsburg Confession to Emperor Charles V at the Diet of Augsburg.
This Concordia Triglotta edition was published in 1917 "as a Memorial of the Quadricentenary Jubilee of the Reformation anno Domini 1921 by resolution of the Evangelical Lutheran Synod of Missouri, Ohio, and Other States," (which later became the Lutheran Church - Missouri Synod).
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.