Aczel, Peter (1988), Non-well-founded sets, CSLI Lecture Notes, vol. 14, Stanford University, Center for the Study of Language and Information, p. 57, ISBN0-937073-22-9, MR0940014, retrieved 2016-10-17.
Aczel, Peter (1988), Non-well-founded sets, CSLI Lecture Notes, vol. 14, Stanford University, Center for the Study of Language and Information, p. 57, ISBN0-937073-22-9, MR0940014, retrieved 2016-10-17.