David Willis (1932 – 2014) was Charles Hodge Professor Emeritus of Systematic Theology at Princeton Theological Seminary and editor of the Studies in Reformed Theology and History series. He was also the author of Notes on the Holiness of God (Eerdmans).
Michael Welker is senior professor at the University of Heidelberg, Germany, and executive director of the Research Center for International and Interdisciplinary Theology. He is the author or editor of dozens of books, including God the Spirit, The Work of the Spirit, God the Revealed, Creation and Reality, What Happens in Holy Communion?, and The Depth of the Human Person.