@article{10_4064_cm91_1_8,
     author = {Richard Penney and Roman Urban},
     title = {Unbounded harmonic functions on
homogeneous manifolds of negative curvature},
     journal = {Colloquium Mathematicum},
     pages = {99--121},
     publisher = {mathdoc},
     volume = {91},
     number = {1},
     year = {2002},
     doi = {10.4064/cm91-1-8},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/cm91-1-8/}
}