http://europepmc.org/abstract/MED/9470817
http://europepmc.org/abstract/MED/8888799
http://europepmc.org/abstract/MED/17118779
http://europepmc.org/abstract/MED/15674332
http://europepmc.org/abstract/MED/15702478
http://europepmc.org/abstract/MED/15956964
http://europepmc.org/abstract/MED/8039618
http://europepmc.org/abstract/MED/11406538