@article{JLT_2013_23_3_JLT_2013_23_3_a2,
     author = {R. Penney and R. Urban },
     title = {Upper {Bound} for the {Heat} {Kernel} on {Higher-Rank} {NA} {Groups}},
     journal = {Journal of Lie theory},
     pages = {655--668},
     publisher = {mathdoc},
     volume = {23},
     number = {3},
     year = {2013},
     url = {http://geodesic.mathdoc.fr/item/JLT_2013_23_3_JLT_2013_23_3_a2/}
}