http://europepmc.org/abstract/MED/12068308
http://europepmc.org/abstract/MED/19789314
http://europepmc.org/abstract/MED/3945555
http://europepmc.org/abstract/MED/22926521
http://europepmc.org/abstract/MED/2108944
http://europepmc.org/abstract/MED/21822268
http://europepmc.org/abstract/MED/21113138