@Article{ MetOuhPal11, author = { Metafune, Giorgio and Ouhabaz, El Maati and Pallara, Diego }, title = { Long time behavior of heat kernels of operators with unbounded drift terms }, journal = { J. Math. Anal. Appl. }, year = { 2011 }, volume = { 377 }, pages = { 170-179 }, URL = { http://cvgmt.sns.it/paper/2397/ }, note = { cvgmt preprint} }