@inproceedings{paul2013$k$-homology,
title={$K$-homology and index theory on contact manifolds},
author={Paul F. Baum, and Erik van Erp},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203403063526790},
booktitle={Acta Mathematica},
volume={213},
number={1},
pages={1-48},
year={2013},
}
Paul F. Baum, and Erik van Erp. $K$-homology and index theory on contact manifolds. 2013. Vol. 213. In Acta Mathematica. pp.1-48. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203403063526790.