http://europepmc.org/abstract/MED/14534542
http://europepmc.org/abstract/MED/9137494
http://europepmc.org/abstract/MED/12204060
http://europepmc.org/abstract/MED/19734198
http://europepmc.org/abstract/MED/14513361
http://europepmc.org/abstract/MED/15616773