Blaeu, Willem Janszoon. "Danubius, fluvius Europae maximus, a fontibus ad ostia, cum omnibus fluminibus, ab utroque latere, in illum defluentibus." Map. Amsterdam: Willem Blaeu, [ca. 1635]. Norman B. Leventhal Map & Education Center, https://collections.leventhalmap.org/search/commonwealth:cj82ks539 (accessed April 23, 2024).