Gopalakrishnan, R. (2010). When the Penny Drops. Portfolio Penguin.
Cita Chicago (17th ed.)Gopalakrishnan, R. When the Penny Drops. Portfolio Penguin, 2010.
Cita MLA (9th ed.)Gopalakrishnan, R. When the Penny Drops. Portfolio Penguin, 2010.
Atenció: Aquestes cites poden no estar 100% correctes.