http://europepmc.org/abstract/MED/9893670
http://europepmc.org/abstract/MED/9049204
http://europepmc.org/abstract/MED/12168936
http://europepmc.org/abstract/MED/9989830
http://europepmc.org/abstract/MED/15012776
http://europepmc.org/abstract/MED/12545816
http://europepmc.org/abstract/MED/25724664
http://europepmc.org/abstract/MED/11149028
http://europepmc.org/abstract/MED/11704835
http://europepmc.org/abstract/MED/10928081
http://europepmc.org/abstract/MED/9464511