http://europepmc.org/abstract/MED/21798893
http://europepmc.org/abstract/MED/26934577
http://europepmc.org/abstract/MED/25234657
http://europepmc.org/abstract/MED/24292195
http://europepmc.org/abstract/MED/28481359
http://europepmc.org/abstract/MED/26619122
http://europepmc.org/abstract/MED/27693639
http://europepmc.org/abstract/MED/27050151