http://europepmc.org/abstract/MED/9600124
http://europepmc.org/abstract/MED/8895682
http://europepmc.org/abstract/MED/29069792
http://europepmc.org/abstract/MED/21837511
http://europepmc.org/abstract/MED/22848674
http://europepmc.org/abstract/MED/22374786