http://europepmc.org/abstract/MED/20376084
http://europepmc.org/abstract/MED/25809997
http://europepmc.org/abstract/MED/27486981
http://europepmc.org/abstract/MED/21828135
http://europepmc.org/abstract/MED/24030381
http://europepmc.org/abstract/MED/26648538
http://europepmc.org/abstract/MED/23443343