John Piper is senior pastor of Bethlehem Baptist Church, Minneapolis and head of Desiring God Ministries. He has written numerous best-selling books which all call readers to spread a passion for the supremacy of God in all things, for the joy of all peoples. His titles include the "Let the nations be glad", "Desiring God", "Tested by fire", "Seeing and savouring Jesus Christ" and "Future Grace" and co-author of Crossway's "Recovering Biblical Manhood and Womanhood".
Wayne A. Grudem is Research Professor of Bible and Theology at Phoenix Seminary, Scottsdale, Arizona. Previously he taught for twenty years at Trinity Evangelical Divinity School, Deerfield, Illinois. He holds degrees from Harvard (BA), Westminster Seminary (MDiv) and Cambridge (PhD), and is a past president of the Evangelical Theological Society. He is the author of a number of books including "Systematic Theology" and "Evangelical Feminism and Biblical Truth".