... in an “unacceptably”smooth Denjoy map and vector field.University of California, Santa Cruz, CA 95064, USAE-mail address: ginzburg@math.ucsc.eduUniversity of California, Santa Cruz, CA, USACurrent ... North-Holland, Amsterdam, 2002.[KH] A. Katok and B. Hasselblatt, Introduction to the Modern Theory of DynamicalSystems, Encyc. of Mathematics and its Applications 54, Cambridge Univ. Press,Cambridge, ... that b|U=0and ∂xf|U=1. This is the required neighborhoodU. (Note that in general we cannot take U = U1∪U2.) The proof of the lemmais completed.6. Proof of Lemma 5.2 The proof of...