Y. Qin et al., THE NONMONOTONIC TWIST MAPS AND BASIC HYPERBOLIC SETS, Science in China. Series A, Mathematics, Physics, Astronomy & Technological Sciences, 41(11), 1998, pp. 1176-1183
The existence of horseshoes for a family of nonmonotonic twist maps is
established. And it is proved that the Hausdorff dimension of the hor
seshoes goes to the dimension of phase space as the parameter goes to
infinity.