http://europepmc.org/abstract/MED/21499247
http://europepmc.org/abstract/MED/26214590
http://europepmc.org/abstract/MED/28481359
http://europepmc.org/abstract/MED/26286987
http://europepmc.org/abstract/MED/24265154
http://europepmc.org/abstract/MED/22842228
http://europepmc.org/abstract/MED/22622578