1.
Serdyuk AS, Stepanets OI, Shydlich AL. Classification of infinitely differentiable periodic functions. Ukr. Mat. Zhurn. [Internet]. 2008Dec.25 [cited 2024Nov.27];60(12):1686–1708. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/3282