http://europepmc.org/abstract/MED/23764841
http://europepmc.org/abstract/MED/22281806
http://europepmc.org/abstract/MED/19228619
http://europepmc.org/abstract/MED/19765000
http://europepmc.org/abstract/MED/24344754
http://europepmc.org/abstract/MED/19554337
http://europepmc.org/abstract/MED/29615461