Yes, the reference is the right one.
See : Thomas Kuhn, The Road since Structure: Philosophical Essays, 1970-1993, Chicago UP (2000), Ch.1 : What Are Scientific Revolutions ? [see : Editor's Introduction, page 6 : "Essay I, "What are Scientific Revolutions?" (ca.1981), consists primarily ..."]
Page 30 :
What characterizes revolutions is, thus, change in several of the taxonomic categories prerequisite to scientific descriptions and generalizations. That change, furthermore, is an adjustment not only of criteria relevant to categorization, but also of the way in which given objects and situations are distributed among preexisting categories.
And yes, according to the full bibiography of Kuhn's works at the end of the book : Publications of Thomas S. Kuhn, page 325-on, there is only one 1981 entry :
What Are Scientific Revolutions ? Occasional Paper #18, Center for Cognitive Science, MIT. Reprinted in The Probabilistic Revolution, vol. I, Ideas in History, edited by Lorenz Kriiger, Lorraine J. Daston and Michael Heidelberger, (1990), MIT Press, pp.7-22; reprinted in this volume as