@article{RMI_2007_2007_1_a37,
     author = {Hyt\"onen, T. P.},
     title = {Littlewood-Paley-Stein theory for semigroups in {UMD} spaces.},
     journal = {Revista matem\'atica iberoamericana},
     pages = {973-1009},
     year = {2007},
     volume = {23},
     number = {3},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/RMI_2007_2007_1_a37/}
}