Search Koha online catalog for books available through Tutt Library. If you have time to wait 3-5 business days, you can also try Prospector.
Tips:
Projekt Gutenberg - DE from Der Spiegel
Google Books Advanced Search - choose language (German), select Full View Only
Briefmarkenserie der Sowjetischen Besatzungszone, 200. Geburtstag von Johann Wolfgang von Goethe (1749—1832) From Wikipedia.