@article{10_4064_sm_24_2_211_226,
     author = {A. Calder\'on and A. Zygmund},
     title = {On higher gradients of harmonic functions},
     journal = {Studia Mathematica},
     pages = {211--226},
     publisher = {mathdoc},
     volume = {24},
     number = {2},
     year = {1964},
     doi = {10.4064/sm-24-2-211-226},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/sm-24-2-211-226/}
}