AGRATINI, O. Book Reviews: “Vijay Gupta, Michael Th. Rassias,” Moments of Linear Positive Operators and Approximation, Springer, 2019, Viii + 96 p., ISBN 978-3-030-19454-3; 978-3-030-19455-0 (ebook). Stud. Univ. Babeş-Bolyai Math. 2019, 64, 601.