@inproceedings{leonid2008determinants,
  title={DETERMINANTS OF ZEROTH ORDER OPERATORS},
  author={Leonid Friedlander, and Victor Guillemin},
  url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20160909103048344927703},
  booktitle={Journal of Differential Geometry},
  volume={78},
  number={1},
  pages={1-12},
  year={2008},
}
             
            
                
Leonid Friedlander, and Victor Guillemin. DETERMINANTS OF ZEROTH ORDER OPERATORS. 2008. Vol. 78. In Journal of Differential Geometry. pp.1-12. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20160909103048344927703.