John Piper is the founder of Desiring God and a teacher at Bethlehem College & Seminary. For 33 years he served as pastor of the Baptist Church in Bethlehem, Minneapolis, Minnesota. He is the author of over 50 books, some of which have been translated and published in Italian.
J.D. Greear is the pastor of The Summit Church, Raleigh-Durham, US, author of numerous books and founder of Greear Ministries. He is also the pastor of Summit Life, a daily broadcast and voice of the podcast Ask Me Anything.