1. [1] Apostol, Tom Introduction to analytic number theory, Springer, Undergraduate Texts in Mathematics (1976)
2. [2] Axler, Christian Über die Primzahl-Zählfunktion, die n-te Primzahl und verallgemeinerte Ramanujan-Primzahlen, Heinrich-Heine-Universität Düsseldorf (Germany) (2013) (Ph. D. Thesis)
3. [3] Axler, Christian On a sequence involving prime numbers, J. Integer Seq., Volume 18 (2015) no. 7, 15.7.6, 13 pages
4. [4] Axler, Christian New estimates for some functions defined over primes, Integers, Volume 18 (2018), A52, 21 pages
5. [5] Axler, Christian Improving the Estimates for a Sequence Involving Prime Numbers, Notes Number Theory Discrete Math., Volume 25 (2019) no. 1, pp. 8-13