@article{10_4064_sm_34_3_299_317,
     author = {Miguel de Guzm\'an},
     title = {A covering lemma with applications to differentiability of measures and singular integral operators},
     journal = {Studia Mathematica},
     pages = {299--317},
     publisher = {mathdoc},
     volume = {34},
     number = {3},
     year = {1970},
     doi = {10.4064/sm-34-3-299-317},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/sm-34-3-299-317/}
}