Brief an Wilhelm von Humboldt vom 29. April 1829 (<bibl xmlns="http://www.tei-c.org/ns/1.0" corresp="https://edition-humboldt.de/RQ7INXBQ">Humboldt 2009a</bibl>, 108–110, Nr. 23); <bibl xmlns="http://www.tei-c.org/ns/1.0" corresp="https://edition-humboldt.de/BH8W3QPH">Rose 1837/1842</bibl>, <ref xmlns="http://www.tei-c.org/ns/1.0" target="https://www.deutschestextarchiv.de/rose_ural01_1837/51">I, 17</ref>–<ref xmlns="http://www.tei-c.org/ns/1.0" target="https://www.deutschestextarchiv.de/rose_ural01_1837/67">33</ref>; <bibl xmlns="http://www.tei-c.org/ns/1.0" corresp="https://edition-humboldt.de/29H3HT3W">Engelhardt 1830</bibl>, <ref xmlns="http://www.tei-c.org/ns/1.0" target="https://www.digitale-sammlungen.de/view/bsb10130333?page=546">526</ref>.