@article{10_4064_ba55_4_9,
     author = {Adam Os/ekowski},
     title = {Sharp {Norm} {Inequalities} for {Martingales} and their
 {Differential} {Subordinates}},
     journal = {Bulletin of the Polish Academy of Sciences. Mathematics},
     pages = {373--385},
     publisher = {mathdoc},
     volume = {55},
     number = {4},
     year = {2007},
     doi = {10.4064/ba55-4-9},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/ba55-4-9/}
}