The Federal Theology: Its Import and Its Regulative Influence
John L. Girardeau
Reformed Academic Press, 55 pages (paperback, 1994; orig. 1881)
This work is a short address the author gave to the Columbia Theological Seminary as part of a larger warning against the devaluing and disappearance of Covenant (or Federal) Theology in Presbyterian theology, from enemies both foreign (German scholasticism) and domestic (Scofieldism). He gives a few short examples of how this is taking place and then goes to a full throat defense of the basic underlying hermeneutic of the Westminster Confession and Reformed theology in general.
I highly recommend this book if you want a better understanding of the place of the covenant in biblical studies and see the prophecies of Dr. Girardeau come to fruition.