Duties of Christian Fellowship by John Owen An excellent study guide for church members. Contains full-text scripture references and discussion questions.
The Everlasting Covenant by Benjamin Keach A sermon on the covenant of Grace.
The Divine Covenants by A. W. Pink Discusses the Everlasting, Adamic, Noahic, Abramhamic, Sinaitic, Davidic, and Messianic, covenants; part eight concerns the Covenant Allegory, wherein Galatians chapter 4 is discussed.