1. Euler, L.Introduction to Analysis of the Infinite,Book I, 137–153. New York: Springer-Verlag. Translated by John D. Blanton
2. Knopp, K. 1990.Theory and Application of Infinite Series, 236–240. New York: Dover Publications. Translated by R.C.H. Young of the 4th German edition of 1947
3. Another Elementary Proof of Euler's Formula for ζ(2n)