@article{JLT_1991_1_2_a11,
     author = {J. Friedrich},
     title = {Extension of {Positive} {Definite} {Functions} on {Lie} {Groups}},
     journal = {Journal of Lie theory},
     pages = {225--234},
     publisher = {mathdoc},
     volume = {1},
     number = {2},
     year = {1991},
     url = {http://geodesic.mathdoc.fr/item/JLT_1991_1_2_a11/}
}