http://europepmc.org/abstract/MED/1324794
http://europepmc.org/abstract/MED/28481359
http://europepmc.org/abstract/MED/15161705
http://europepmc.org/abstract/MED/10091733
http://europepmc.org/abstract/MED/1347094
http://europepmc.org/abstract/MED/7549812
http://europepmc.org/abstract/MED/7767998