1. Brigham E, Gapenski L. Financial management—theory and practice. 8th ed. The Dryden Press, 1997. p. 396–403.
2. Erbs DG, Klein SA, Beckman WA. Estimation of degree-days and ambient temperature bin data from monthly-average temperatures. ASHRAE Journal 1983;25(6):60–5.
3. Harrison R, Mortimer N, Smarason O. Geothermal heating—a handbook of engineering economics. Oxford: Pergamon Press, 1990. p. 315–47.
4. Keown A, Scott D, Martin J, Petty W. Basic financial management. 7th ed. Prentice–Hall International, 1996. p. 316–23.
5. Knight KM, Klein SA, Duffie JA. A methodology for the synthesis of hourly weather data. Solar Energy 1991;46(2):109–20.