APA (7th ed.) Citation

Sinek, S. (2011). Start with why: How great leaders inspire everyone to take action. Portfolio Penguin.

Chicago Style (17th ed.) Citation

Sinek, Simon. Start with Why: How Great Leaders Inspire Everyone to Take Action. London [etc.]: Portfolio Penguin, 2011.

MLA (9th ed.) Citation

Sinek, Simon. Start with Why: How Great Leaders Inspire Everyone to Take Action. Portfolio Penguin, 2011.