Bolzano, B. (2018). Purely Analytical Proof of a Claim, that Between Each Two Values Resulting in Opposite Signs, There is a Real Equation Element. Annales Universitatis Paedagogicae Cracoviensis | Studia Ad Didacticam Mathematicae Pertinentia, 9(1), 197–217. Retrieved from https://didacticammath.uken.krakow.pl/article/view/4315