Miller, Philip B. «Anxiety and Abstraction: Kleist and Brentano on Caspar David Friedrich». Art Journal, 33, 3, Spring 1974, p. 205–210. DOI: 10.2307/775783.
Forster-Hahn, Françoise «Recent Scholarship on Caspar David Friedrich». The Art Bulletin, 58, 1, març 1976, p. 113–116. DOI: 10.2307/3049469.