Rosenthal, E. (1971). Plus ultra, non plus ultra, and the Columnar Device of Emperor Charles V. Journal of the Warburg and Courtauld Institutes, 34, 204-228.

Rosenthal, E. (1973). The Invention of the Columnar Device of Emperor Charles V at the Court of Burgundy in Flanders in 1516. Journal of the Warburg and Courtauld Institutes, 36, 198-230.