finance and options - Math bibliographies - in Harvard style

In-text: (Hull and Hull, 1997)

Your Bibliography: Hull, J. and Hull, J., 1997. Options, futures, and other derivatives. Upper Saddle River, NJ: Prentice Hall.

there is a 95% chance that a normally distributed variable lies with 1.96 standard deviations of its mean

In-text: (Hull, 2008)

Your Bibliography: Hull, J., 2008. Fundamentals of futures and options markets. Upper Saddle River, N.J.: Pearson Prentice Hall.

In-text: (Hull, 2009)

Your Bibliography: Hull, J., 2009. Options, futures and other derivatives. 7th ed. Upper Saddle River, N.J.: Pearson Prentice Hall, p.283.