Now retired, Bill Johnson has taught heating, air conditioning, and refrigeration for more than two decades in various technical colleges and factory schools. A graduate of Southern Technical Institute, a branch of Georgia Tech in Atlanta, Georgia, he has also served as Service Manager for a major manufacturer for six years.

Mr. Johnson owned his own HVAC/R business for 10 years and has been a member of the Refrigeration Service Engineers Society and the American Society of Heating Refrigerating Air Conditioning Engineers.

His authoring credits include three major textbooks on the market today as well as their ancillary materials. He also writes a monthly article - BTU Buddy - that is available online.

Robert Henderson is a prolific non-graduate from a range of prestigious Australian universities and an actual graduate of Griffith University's Queensland College of Art.

Robert lives in Brisbane with his partner and two young children who help him with his work and make sure he never has to eat a sandwich by himself.

John Eldredge is a bestselling author, a counselor, and a teacher. He is also president of Ransomed Heart, a ministry devoted to helping people discover the heart of God, recover their own hearts in God’s love, and learn to live in God’s kingdom. John and his wife, Stasi, live near Colorado Springs, Colorado.