The following formula is involved in the calculation of present value interest factors:

Present value interest factor:
where R is the periodic interest rate and N is the number of periods.

The following references can be used to cite this present value interest factor (pvif) calculator:
 Soper, D.S. (2017) "Present Value Interest Factor (PVIF) Calculator (Online Software)", http://www.danielsoper.com/fincalc. 
 Gitman, L. (2011). "Principles of Managerial Finance (13th Edition)", Upper Saddle River, NJ: Prentice Hall. 