@article{MS2_1982__50_166781,
     author = {Jorgen Hoffmann-Jorgensen},
     title = {A general },
     journal = {Mathematica Scandinavica},
     pages = {55--65},
     year = {1982},
     volume = {50},
     zbl = {0494.54013},
     url = {http://geodesic.mathdoc.fr/item/MS2_1982__50_166781/}
}