@article{10_4153_CJM_1986_058_7,
     author = {Bruckner, A. M. and Laczkovich, M. and Petruska, G. and Thomson, B. S.},
     title = {Porosity and {Approximate} {Derivatives}},
     journal = {Canadian journal of mathematics},
     pages = {1149--1180},
     year = {1986},
     volume = {38},
     number = {5},
     doi = {10.4153/CJM-1986-058-7},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1986-058-7/}
}