The constitution of FELSISA states the following regarding adherence to the Lutheran Confessions:
22.214.171.124 As true and binding statement and exposition of the Holy Scriptures the Symbolical Books of the Evangelical Lutheran Church are accepted; that is, the three Ecumenical Symbols (the Apostles’ Creed, the Nicene Creed, the Athanasian Creed) the Unaltered Augsburg Confession and its Apology, the Smalcald Articles, the Small and the Large Catechisms of Dr. Martin Luther and the Formula of Concord. (The Lutheran Confession)
The Lutheran Confessions can be found in the Book of Concord on the following website: http://bookofconcord.org
For a more recent translation a copy can be purchased at:
Concordia Publishing House. Concordia: The Lutheran Confessions-A Reader’s Edition of the Book of Concord – 2nd edition.