APA (7th ed.) Citation

Stone, Patton, & Heen. (1999). Difficult conversations: How to discuss what matters most. Viking.

Chicago Style (17th ed.) Citation

Stone, Patton, and Heen. Difficult Conversations: How to Discuss What Matters Most. New York: Viking, 1999.

MLA (8th ed.) Citation

Stone, et al. Difficult Conversations: How to Discuss What Matters Most. Viking, 1999.