@article{700126,
     title = {On the smoothness of the solutions to the elliptic systems},
     booktitle = {Equadiff 6},
     series = {GDML\_Books},
     publisher = {J. E. Purkyn\v e University, Department of Mathematics},
     address = {Brno},
     year = {1986},
     pages = {[459]-464},
     mrnumber = {MR0881672},
     url = {http://dml.mathdoc.fr/item/700126}
}

Koshelev, Alexander Ivanovich. On the smoothness of the solutions to the elliptic systems, dans Equadiff 6, GDML_Books,  (1986), pp. [459]-464. http://gdmltest.u-ga.fr/item/700126/