Engel is founder and president of Development Associates International and retired distinguished professor in the graduate programs at Eastern University, where he founded the Center for Organizational Excellence. He has ministered around the world as a consultant, trainer and leadership-development expert and is well known for his books and writings on world evangelization.
William A. Dyrness is professor of theology and culture at Fuller Theological Seminary. He is a former missionary and the author of several books, including The Earth Is God's: A Theology of American Culture, Learning About Theology from the Third World, How Does America Hear the Gospel? and Reformed Theology and Visual Culture.