http://europepmc.org/abstract/MED/19412570
http://europepmc.org/abstract/MED/10522720
http://europepmc.org/abstract/MED/17097223
http://europepmc.org/abstract/MED/11161385
http://europepmc.org/abstract/MED/12021900
http://europepmc.org/abstract/MED/7820300
http://europepmc.org/abstract/MED/10923915
http://europepmc.org/abstract/MED/18343945