When compiling a short-title catalogue, Paul Valkema Blouw was confronted with a large number of ‘problem cases’. By minute analysis and drawing from his extensive knowledge and his unrivalled typographic memory, he could attribute a surprising number of these publications to a printer and established the periods when and places where they must have been printed.The present collection of papers is of paramount importance to scholars engaged in research of the sixteenth century, whether in the field of church history, national history or book history.