author
1865–1933
A Dutch Reformed minister and religious writer, he moved between scholarship and public church life. His surviving works show a strong interest in theology, church history, and Protestant thought.

by J. A. (Jan Anthony) Cramer, J. H. (Jan Hendrik) Gerretsen, Frank van Gheel-Gildemeester, P. J. Molenaar, J. C. Schuller, Hendrik Anne Constantijn Snethlage, A. J. A. Vermeer, W. L. Welter
Born in the 1860s and active around the turn of the twentieth century, Gerretsen wrote in Dutch on theological subjects and historical religious figures. Catalog and bookseller records connect him with works such as Florentius Radewijns, Micronius, Liturgie, and Rechtvaardigmaking bij Paulus, suggesting a writer deeply engaged with church history, doctrine, and worship.
He was also known in Dutch church life beyond the page. A Dutch Wikipedia list of court preachers identifies Jan Hendrik Gerretsen as a hofpredikant, or court preacher, in the early twentieth century, and notes his role in the 1909 baptism of Princess Juliana.
Some reference pages disagree on his exact life dates, and I could not confirm a reliable portrait image from the sources available here. What does come through clearly is the outline of a minister-author whose books were rooted in Protestant theology and whose career reached into the religious life of the Dutch royal court.