http://europepmc.org/abstract/MED/21904853
http://europepmc.org/abstract/MED/22706669
http://europepmc.org/abstract/MED/27997717
http://europepmc.org/abstract/MED/22489043
http://europepmc.org/abstract/MED/19609284
http://europepmc.org/abstract/MED/25005031
http://europepmc.org/abstract/MED/24325359