http://europepmc.org/abstract/MED/9816033
http://europepmc.org/abstract/MED/7882351
http://europepmc.org/abstract/MED/18559592
http://europepmc.org/abstract/MED/27566247
http://europepmc.org/abstract/MED/11280771
http://europepmc.org/abstract/MED/19375815