@inproceedings{jonathan1984adjoint,
  title={Adjoint boundary value problems for the biharmonic equation on$C$^{$1$}domains in the plane},
  author={Jonathan Cohen, and John Gosselin},
  url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203520208505432},
  booktitle={Arkiv for Matematik},
  volume={23},
  number={1},
  pages={217-240},
  year={1984},
}
             
            
                
Jonathan Cohen, and John Gosselin. Adjoint boundary value problems for the biharmonic equation on$C$^{$1$}domains in the plane. 1984. Vol. 23. In Arkiv for Matematik. pp.217-240. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203520208505432.