Reference. Sketches of an Elephant [johnstone-2002-sketches]

@book{johnstone-2002-sketches,
	title = {Sketches of an Elephant},
	author = {Johnstone, Peter},
	year = {2002},
	publisher = {Oxford University Press},
	note = {\url{https://ncatlab.org/nlab/show/Sketches+of+an+Elephant}}
}