http://europepmc.org/abstract/MED/9600124
http://europepmc.org/abstract/MED/11289147
http://europepmc.org/abstract/MED/1453686
http://europepmc.org/abstract/MED/21837511
http://europepmc.org/abstract/MED/22848674
http://europepmc.org/abstract/MED/27609830