Ries , A. &. (1990). Bottom-up marketing. Penguin.
Cita Chicago (17th ed.)Ries , Al &Trout. Bottom-up Marketing. New York: Penguin, 1990.
Cita MLA (9th ed.)Ries , Al &Trout. Bottom-up Marketing. Penguin, 1990.
Atenció: Aquestes cites poden no estar 100% correctes.