http://europepmc.org/abstract/MED/18551309
http://europepmc.org/abstract/MED/16931951
http://europepmc.org/abstract/MED/9676855
http://europepmc.org/abstract/MED/18752119
http://europepmc.org/abstract/MED/20332486
http://europepmc.org/abstract/MED/8523819
http://europepmc.org/abstract/MED/10584701