Impossible object (English Wikipedia)

Aigner, Martin; Ziegler, Günter M. (2018). "Chapter 15: The Borromean Rings Don't Exist". Proofs from THE BOOK (6th ed.). Springer. pp. 99–106. doi:10.1007/978-3-662-57265-8_15. ISBN 978-3-662-57265-8.
Penrose, LS; Penrose, R. (1958). "Impossible objects: A special type of optical illusion". British Journal of Psychology. 49 (1): 31–33. doi:10.1111/j.2044-8295.1958.tb00634.x. PMID 13536303.
Penrose, Roger (1992). "On the Cohomology of Impossible Figures". Leonardo. 25 (3, 4). The MIT Press: 245–247. doi:10.2307/1575844. JSTOR 1575844. S2CID 125905129.

fink.com (Global: low place; English: low place)

Penrose, Roger (1992). "On the Cohomology of Impossible Figures". Leonardo. 25 (3, 4). The MIT Press: 245–247. doi:10.2307/1575844. JSTOR 1575844. S2CID 125905129.

Penrose, LS; Penrose, R. (1958). "Impossible objects: A special type of optical illusion". British Journal of Psychology. 49 (1): 31–33. doi:10.1111/j.2044-8295.1958.tb00634.x. PMID 13536303.

Penrose, Roger (1992). "On the Cohomology of Impossible Figures". Leonardo. 25 (3, 4). The MIT Press: 245–247. doi:10.2307/1575844. JSTOR 1575844. S2CID 125905129.

Khoh, Chih W.; Kovesi, Peter (February 1999). "Animating Impossible Objects". Archived from the original on 28 May 2015. Retrieved 10 February 2014.

Khoh, Chih W.; Kovesi, Peter (February 1999). "Animating Impossible Objects". Archived from the original on 28 May 2015. Retrieved 10 February 2014.