Our paper on SUBTLEX-NL can be found here and should be cited as:
Keuleers, E., Brysbaert, M. & New, B. (2010). SUBTLEX-NL: A new frequency measure for Dutch words based on film subtitles. Behavior Research Methods, 42(3), 643-650.
An introduction in Dutch to the SUBTLEX-NL database can be found here.
You can do an online search for the SUBTLEX-NL frequencies of your words here.
A Dutch introduction to the online search engine can be found here.