http://europepmc.org/abstract/MED/21552959
http://europepmc.org/abstract/MED/7628866
http://europepmc.org/abstract/MED/15538112
http://europepmc.org/abstract/MED/7620944
http://europepmc.org/abstract/MED/14670539
http://europepmc.org/abstract/MED/7767983
http://europepmc.org/abstract/MED/9610789
http://europepmc.org/abstract/MED/8020137