Alvarez, Josefina, and Hamed M. Obiedat. 2004. “Characterizations of the Schwartz Space and the Beurling-Björck Space 𝔖ω”. CUBO, A Mathematical Journal 6 (4):167-83. https://www.perspectivasdelacomunicacion.cl/ojs/index.php/cubo/article/view/1559.