Albert Repholtz: Thorvaldsen og Nysø, Copenhagen 1911, p. 27 (the clay model was cast in plaster on 16.8.1839).
Thiele IV, p. 70. Thiele writes that the bust is begun after the return from the trip to Kullen and before Thorvaldsen’s departure for Nysø, which is dated differently by Thiele and by Stampe; see also presumably 13.7.1839.
Else Kai Sass: Thorvaldsens Portrætbuster, Copenhagen 1963-65, Vol. II, p. 319-325, 379, 387.