This is the sixth volume in the ongoing complete edition and the second devoted to the Köthen correspondence. The volume assembles 103 letters and 26 supplements (including some minor Academy publications) from the period 1627-1629. As in the first volume (Tübingen 1993), the critical edition of the documents draws very largely on manuscript sources. They are provided with annotations and supplemented by illustrations, a glossary, an index of subjects and an index of persons.