Who proved that $\pi(n) < 1.25506\frac{n}{ln(n)}$?
I am trying to write a paper that relies on this inequality, but I cannot find the citation and I want to be certain the inequality was proven.
Edit: I looked at the Rosser and Schoenfeld paper "Approximate formulas for some functions of prime numbers" and it mentions the inequality as corollary 1 but no proof is provided
I also looked at the Wikipedia page on the Prime-counting function and it gives a crude explanation. I would be a fool to quote Wikipedia in my paper.