Escher, M. C. (Maurits Cornelis). Ascending and descending. Mar 1960. Web. 28 Feb 2021. <https://ark.digitalcommonwealth.org/ark:/50959/3r076s51v>.

Escher, M. (1960, March). Ascending and descending [Print]. Retrieved from https://ark.digitalcommonwealth.org/ark:/50959/3r076s51v

Escher, M. C. (Maurits Cornelis). "Ascending and descending." Print. March 1960. Digital Commonwealth, https://ark.digitalcommonwealth.org/ark:/50959/3r076s51v (accessed February 28, 2021).