Rys, Petr, and Tomáš Zdráhal. “Slow Divergence of the Harmonic Series”. Annales Universitatis Paedagogicae Cracoviensis Studia Mathematica 3 (May 27, 2003): 233–235. Accessed October 30, 2026. https://studmath.uken.krakow.pl/article/view/13494.