http://europepmc.org/abstract/MED/7670111
http://europepmc.org/abstract/MED/9531609
http://europepmc.org/abstract/MED/23989669
http://europepmc.org/abstract/MED/7579381
http://europepmc.org/abstract/MED/9515810
http://europepmc.org/abstract/MED/10086736
http://europepmc.org/abstract/MED/9369426
http://europepmc.org/abstract/MED/16960149
http://europepmc.org/abstract/MED/22619049