@article{10_4064_cm103_2_5,
     author = {Jacek Zienkiewicz},
     title = {Estimates for
  the {Hardy{\textendash}Littlewood} maximal function
  on the {Heisenberg} group},
     journal = {Colloquium Mathematicum},
     pages = {199--205},
     publisher = {mathdoc},
     volume = {103},
     number = {2},
     year = {2005},
     doi = {10.4064/cm103-2-5},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/cm103-2-5/}
}