http://europepmc.org/abstract/MED/27939411
http://europepmc.org/abstract/MED/28481359
http://europepmc.org/abstract/MED/21381030
http://europepmc.org/abstract/MED/20826764
http://europepmc.org/abstract/MED/21882256
http://europepmc.org/abstract/MED/23267135
http://europepmc.org/abstract/MED/21435433