Habiburrohman, Muhammad, and Dinni Rahma Oktaviani. “Boundedness of Pseudo-Differential Operator for S0 Class”. Journal of Natural Sciences and Mathematics Research, vol. 6, no. 2, Dec. 2020, pp. 43-48, https://journal.walisongo.ac.id/index.php/JNSMR/article/view/11219.