In my P.H.D. thesis especially Paul’s epistle to the Galatians was discussed. Thereafter other small Pauline epistles attracted my attention. The epistles to the Philippians, the Thessalonians, to Philemon and the Pastoral Epistles were discussed by me in commentaries. The problem of the (in-)authenticity of some epistles deserved particular notice, and I wrote some articles about this item. By my collaboration to the Biografisch Lexicon voor de Geschiedenis van het Nederlandse Protestantisme I got acquainted with the work of New Testament scholars from former days. I wrote articles about fifteen ministers and professors who had made their name. About two of the, Willem Christiaan van Manen and Adriaan van Veldhuizen, I wrote a book.

In the course of time I was more and more fascinated by the epistle to the Philippians and by the town Philippi where these people had lived. I visited it frequently and I tried to collect data as much as possible. This led to a study about Philippi that was published in 2009. A more expanded English translation was published in 2013. It had struck me that in Christianity, in any case in Philippi, diverse elements were adopted from older religions. I discovered the same phenomenon in the Islam. We can find several elements from older religions in the Qor’an as well. I would like to do research about this phenomenon in both Christanity and in the Islam. The question that is behind this phenomenon, is what then is the uniqueness of Christianity and of the Islam, if so many elements were adopted from older religions. In the beginning of 2015 I published a Dutch translation of the Qor’an. In the beginning of 2016 a second edition was published by Skandalon, a third edition in 2019. In 2017 Skandalon published a  separate volume with a commentary on the Qor’an. The second edition was published in 2021. Moreover I wrote a book on Jezus in christendom en islam, Skandalon 2021.