http://europepmc.org/abstract/MED/21390130
http://europepmc.org/abstract/MED/16404744
http://europepmc.org/abstract/MED/21680795
http://europepmc.org/abstract/MED/27683039
http://europepmc.org/abstract/MED/25790293
http://europepmc.org/abstract/MED/25105841