Jaap was a distinguished and brilliant mathematician, an inspiring teacher, and a passionate researcher well into old age. He lives on through his articles and books, in which he made lasting contributions to functional analysis, complex function theory, and asymptotic analysis. He was also a warm and dedicated colleague, who made significant contributions to our institute. We cherish his legacy and will never forget his inspiring example.

He received various honors, including his appointment as a Fellow of the American Mathematical Society in 2012, the Lester R. Ford Prize (1987) and the Chauvenet Prize (1989) from the MAA, and he was named a Fellow of the American Association for the Advancement of Science (AAAS) in 1960. Additionally, he held several positions at the Royal Netherlands Academy of Arts and Sciences (KNAW), where he ultimately served as Chair of the Mathematics Section from 1994 to 1996.