@article{SF_1980__20_134403,
     author = {A. Janssen},
     title = {A general purity law for convolution semigroups with discrete {Levy} measure.},
     journal = {Semigroup forum},
     pages = {55--72},
     publisher = {mathdoc},
     volume = {20},
     year = {1980},
     zbl = {0442.60015},
     url = {http://geodesic.mathdoc.fr/item/SF_1980__20_134403/}
}