@article{702337,
     title = {The Helmholtz decomposition and the weak Neumann problem in $L^q$
               },
     booktitle = {Equadiff 7},
     series = {GDML\_Books},
     publisher = {BSB B.G. Teubner Verlagsgesellschaft},
     address = {Leipzig},
     year = {1990},
     pages = {199-201},
     zbl = {0723.35024},
     url = {http://dml.mathdoc.fr/item/702337}
}

Simader, C. G. The Helmholtz decomposition and the weak Neumann problem in $L^q$
               , dans Equadiff 7, GDML_Books,  (1990), pp. 199-201. http://gdmltest.u-ga.fr/item/702337/