Vasu, A. C., V. V. Subrahmanya Sastri, and C. S. Venkataraman. “On a New Class of Convolutions and Euler Products”. The Journal of the Indian Mathematical Society, vol. 54, no. 1-4, Dec. 1989, pp. 219-32, https://informaticsjournals.co.in/index.php/jims/article/view/21899.