http://europepmc.org/abstract/MED/7544647
http://europepmc.org/abstract/MED/7632963
http://europepmc.org/abstract/MED/23900870
http://europepmc.org/abstract/MED/21356189
http://europepmc.org/abstract/MED/7833469
http://europepmc.org/abstract/MED/7727766
http://europepmc.org/abstract/MED/8603008
http://europepmc.org/abstract/MED/22994152