In addition to the various state and university libraries in Germany, there are four major research libraries that are of interest for research on the Reformation and early modern religious culture: the Forschungsbibliothek Gotha, the Johannes a Lasco Bibliothek in Emden, the Reformationsgeschichtliche Forschungsbibliothek in Wittenberg, and the Herzog August Bibliothek in Wolfenbüttel. All of these institutions offer support for researchers. If you are interested in doing research in Wolfenbüttel, please check out the many options listed on their website.