@article{10_4064_sm_94_1_81_95,
     author = {Jacek Dziuba\'nski and Andrzej Hulanicki},
     title = {On semigroups generated by left-invariant positive differential operators on nilpotent {Lie} groups},
     journal = {Studia Mathematica},
     pages = {81--95},
     publisher = {mathdoc},
     volume = {94},
     number = {1},
     year = {1989},
     doi = {10.4064/sm-94-1-81-95},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/sm-94-1-81-95/}
}