http://europepmc.org/abstract/MED/15376262
http://europepmc.org/abstract/MED/9566701
http://europepmc.org/abstract/MED/19026650
http://europepmc.org/abstract/MED/7515658
http://europepmc.org/abstract/MED/20544848
http://europepmc.org/abstract/MED/9731892
http://europepmc.org/abstract/MED/22287596