@article{CMH_1976__51_139645,
     author = {Jan G. Krzyz},
     title = {Convolution and {Quasiconformal} {Extension}},
     journal = {Commentarii mathematici Helvetici},
     pages = {99--104},
     publisher = {mathdoc},
     volume = {51},
     year = {1976},
     zbl = {0323.30022},
     url = {http://geodesic.mathdoc.fr/item/CMH_1976__51_139645/}
}