Paideia Press has been reprinting and publishing Dutch Reformed works for the past 40 years. Recently they have made PDFs of most of their publications available for download. You can find the complete list, with links, here. These include some of the most helpful biblical theological works from DeGraaf and Ridderbos, as well as many of the works of Kuyper and Bavinck. The following are some of the more difficult volumes to find in electronic format, as they can only be found in PDF format at Paideia's website.

DeGraaf, S.G.. Promise and Deliverance I: From Creation To The Conquest Of Canaan PDF (pdf file 14 meg) DeGraaf, S.G.. Promise and Deliverance II: The failure of Israel's Theocracy PDF (pdf file 17 meg) DeGraaf, S.G.. Promise and Deliverance III: Christ's Ministry and Death PDF (pdf file 15 meg) DeGraaf, S.G.. Promise and Deliverance IV (Christ and the Church) PDF (pdf file 10 meg) DeGraaff, A.H.. The Natrue and Aim of Christian Education PDF (pdf file 1 meg) Ridderbos, . Modern Thinkers Series: Bultmann PDF (pdf file 562 k) Ridderbos, H.. Studies in Scripture and its Authority PDF (pdf file 5 meg) Ridderbos, H.. The Coming of the Kingdom PDF (pdf file 25 meg) Ridderbos, H.N.. When the Time Had Fully Come: Studies in the New Testament Theology PDF (pdf file 4 meg)