http://europepmc.org/abstract/MED/15131047
http://europepmc.org/abstract/MED/8395678
http://europepmc.org/abstract/MED/22609129
http://europepmc.org/abstract/MED/8082516
http://europepmc.org/abstract/MED/1647768
http://europepmc.org/abstract/MED/9924427
http://europepmc.org/abstract/MED/16235243