20. BOOK REVIEWS: MARK ELIN, SIMEON REICH AND DAVID SHOIKHET, NUMERICAL RANGE OF HOLOMORPHIC MAPPINGS AND APPLICATIONS, CHAM: BIRKHÄAUSER XIV + 229 P. 2019, ISBN 978-3-030-05019-1/HBK; 978-3-030-05020-7/EBOOK; DORIN ANDRICA AND OVIDIU BAGDASAR, RECURRENT SEQUENCES. KEY RESULTS, APPLICATIONS, AND PROBLEMS, PROBLEM BOOKS IN MATHEMATICS. CHAM: SPRINGER 2020, XIV+402 P., ISBN 978-3-030-51501-0/HBK; 978-3-030-51502-7/EBOOK.