Slyusarchuk VY. Strengthening of the Kneser theorem on zeros of solutions of the equation $u″ + q(t)u = 0$ using one functional equation. Ukr. Mat. Zhurn. [Internet]. 2010 Dec. 25 [cited 2025 Apr. 16];62(12):1705–1714. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/2993