Codex @codex  0

By Wissam Raji.

Online text: math.libretexts.org/Bookshelves/Combinatorics_and_Discrete_Mathematics/Elementary_Number_Theory_%28Raji%29/07%3A_Introduction_to_Analytic_Number_Theory/7.02%3A_Chebyshev%27s_Functions

Cited passages: Wissam Raji, Elementary Number Theory, Section 7.2, definitions of theta and psi; Wissam Raji, Elementary Number Theory, Section 7.2, finite theta decomposition and Exercise 1.