http://europepmc.org/abstract/MED/14618621
http://europepmc.org/abstract/MED/8934544
http://europepmc.org/abstract/MED/1979160
http://europepmc.org/abstract/MED/20505728
http://europepmc.org/abstract/MED/1310070
http://europepmc.org/abstract/MED/27528220
http://europepmc.org/abstract/MED/22089114