Online text: dlmf.nist.gov/25.6
Part of Chapter 25, Zeta and Related Functions, credited to T. M. Apostol. The site release date is not treated as the chapter publication year.
Cited passages: §25.6(i), equations 25.6.1–25.6.2: positive even arguments.
Online text: dlmf.nist.gov/27.9
Part of Chapter 27, Functions of Number Theory, credited to T. M. Apostol. The site version release date is not treated as the chapter publication year.