http://europepmc.org/abstract/MED/7606737
http://europepmc.org/abstract/MED/8242071
http://europepmc.org/abstract/MED/12414520
http://europepmc.org/abstract/MED/10980114
http://europepmc.org/abstract/MED/22287596
http://europepmc.org/abstract/MED/12920223