http://europepmc.org/abstract/MED/23633455
http://europepmc.org/abstract/MED/23791828
http://europepmc.org/abstract/MED/25846551
http://europepmc.org/abstract/MED/9796975
http://europepmc.org/abstract/MED/7795636
http://europepmc.org/abstract/MED/21720365
http://europepmc.org/abstract/MED/11240689