http://europepmc.org/abstract/MED/21381030
http://europepmc.org/abstract/MED/25720322
http://europepmc.org/abstract/MED/22653804
http://europepmc.org/abstract/MED/21882256
http://europepmc.org/abstract/MED/23104009
http://europepmc.org/abstract/MED/22923510
http://europepmc.org/abstract/MED/21435433