KVK [Karlsruhe Virtual Catalog]. Search for a topic, place, title, in various German (and other) libraries at this link: Karlsruher Virtueller Katalog. Click the library of interest or search them all. You may choose "Digital resources" only. For example, a Freitext search "Peder Jensen Hegelund" "Nur digitale Medien suchen" [digital resources only] produced many references to works by this man that are online.