Vgl. z. B. Humboldt an <persName xmlns="http://www.tei-c.org/ns/1.0" ref="https://edition-humboldt.de/H0012589 http://d-nb.info/gnd/11862783X">Altenstein</persName>, <placeName xmlns="http://www.tei-c.org/ns/1.0" ref="https://edition-humboldt.de/H0005221 https://www.geonames.org/2950159">Berlin</placeName>, 5. September 1828, Krakau, Biblioteka Jagiellońska, Sgl. Autographa.