The cologarithm in base b of a number is also equal to the logarithm of the same number having the reciprocal of b as the base:
- Hall, Arthur Graham; Frink, Fred Goodrich (January 1909). "Chapter IV. Logarithms  Cologarithms". Written at Ann Arbor, Michigan, USA. Trigonometry. Part I: Plane Trigonometry. New York, USA: Henry Holt and Company / Norwood Press / J. S. Cushing Co. - Berwick & Smith Co., Norwood, Massachusetts, USA. p. 36. Retrieved 2017-08-12.
- "Cologarithm". Merriam-Webster Dictionary. Archived 16 February 2007 at the Wayback Machine.
- "Cologarithm". Wolfram MathWorld.