«Karel Schwarzenberg, Czech diplomat, 1937–2023». Financial Times. 18. november 2023. «Karel goes to rest as his serene highness, (twice) Prince Schwarzenberg, Count of Sulz, Princely Landgrave of Klettgau and Duke of Krumlov.»
Regional Database of the Central Bohemian Research Library in Kladno, SVKKL authority ID p0011773-Schwarzenberg-Karel-1937, besøkt 20. juni 2023[Hentet fra Wikidata]