@inproceedings{vladimir2003the,
  title={The highest smoothness of the Green function implies the highest density of a set},
  author={Vladimir V. Andrievskii},
  url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203610987113840},
  booktitle={Arkiv for Matematik},
  volume={42},
  number={2},
  pages={217-238},
  year={2003},
}
             
            
                
Vladimir V. Andrievskii. The highest smoothness of the Green function implies the highest density of a set. 2003. Vol. 42. In Arkiv for Matematik. pp.217-238. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203610987113840.