http://europepmc.org/abstract/MED/2680062
http://europepmc.org/abstract/MED/24793135
http://europepmc.org/abstract/MED/22142829
http://europepmc.org/abstract/MED/24436047
http://europepmc.org/abstract/MED/21412928
http://europepmc.org/abstract/MED/20068162
http://europepmc.org/abstract/MED/24332040