http://europepmc.org/abstract/MED/15221786
http://europepmc.org/abstract/MED/11329143
http://europepmc.org/abstract/MED/17692090
http://europepmc.org/abstract/MED/9665415
http://europepmc.org/abstract/MED/16322298
http://europepmc.org/abstract/MED/8630996
http://europepmc.org/abstract/MED/16229746
http://europepmc.org/abstract/MED/11079169