Corollary 4 (p. 123) in Hlawka, Taschner, and Schoissengeier, *Geometric and Analytic Number Theory*

Theorem 7.10 (p. 111) in Ayoub, *An Introduction to the Analytic Theory of Numbers*.

Theorem 3.4.5 (p. 134) in Jameson, *The Prime Number Theorem*.

Theorem 5.20 (p. 239) in Narkiewicz, *The Development of Prime Number Theorey from Euclid to Hardy and Littlewood* 

Theorem 5.9 (p. 100) in Bateman and Diamond, *Analytic Number Theory: An Introductory Course*.