http://europepmc.org/abstract/MED/7563186
http://europepmc.org/abstract/MED/22669776
http://europepmc.org/abstract/MED/27566247
http://europepmc.org/abstract/MED/22422578
http://europepmc.org/abstract/MED/23887298
http://europepmc.org/abstract/MED/27530957