Adorno began writing an introduction to a collection of poetry by Rudolf Borchardt, which was connected with a talk entitled "Charmed Language," delivered in Zurich, followed by a talk on aesthetics in Paris where he met Beckett again. Beginning in October 1966, Adorno took up work on "Aesthetic Theory". In June 1969 he completed "Catchwords: Critical Models". During the winter semester of 1968–69 Adorno was on sabbatical leave from the university and thus able to dedicate himself to the completion of his book of aesthetics.