A revised and updated version of
Abraham Kuyper: An Annotated Bibliography 1857-2010 by Tjitze Kuipers (2011)
You can buy a printed edition of this book on the site of the publisher.
1916
Open schrijven van het Bestuur der Patroonsvereeniging aan de Christelijke patroon[s] in Nederland.
In: Boaz. 25 (1916), no. 12, pp. [217]–231.
The open letter of 1892 was reprinted in a special issue of Boaz’s monthly paper celebrating its twenty-fifth anniversary. (The Association of Dutch Employers “Boaz” was founded in November 1891.) In the issue Kuyper was named as the author of this letter.