1999 March 15, John Clute with John Grant, The Encyclopedia of Fantasy, Macmillan, →ISBN, →OL, keyword "Escher, M(aurits) C(ornelis)", page 322:
[…] and the more subtly disconcerting Penrose stairs in "Ascending and Descending" (1960), where cowled figures plod around a quadrilateral loop of staircase going forever up, or down.
2011 June 27, Waka Nakanishi, Taisuke Matsuno, Junji Ichikawa, Hiroyuki Isobe, “llusory Molecular Expression of “Penrose Stairs” by an Aromatic Hydrocarbon”, in Angewandte Chemie International Edition, volume 50, number 27, →DOI, pages 6048–6051:
A combination of two helical molecules and two twisting covalent axes in the form of a macrocycle conjures an illusory molecular object that has a seemingly impossible molecular structure, that is, an endlessly descending circle that consists of an sp2-carbon network, which can be regarded as the molecular expression of Penrose stairs.
2012 April 16, Rob Coley with Dean Lockwood, Cloud Time, Alresford: Zero Books, →ISBN, →OL, page 5:
Inception contains a set of Penrose stairs which handily illustrate the disjunctive Baroque-Cartesian synthesis described here.
possibly a reference to Penrose's specific stairs, but probably generic
1985, Jack Weber, Computers[1], New York: Arco, →ISBN, →OL, page 62:
All three — the Penrose triangle, the devil's pitchfork and the Penrose stairs — can be instantly recognized as impossible objects: our brains do it very easily, but how could we set about programming a computer to see that they are visual frauds?
2012, Christopher Davis, Pieces of Thought→ISBN, page 34:
The world just escalated, climbing up the Penrose stairs motorized and unmotivated we've populated this big blue sphere with war […]
