http://europepmc.org/abstract/MED/21225871
http://europepmc.org/abstract/MED/22327622
http://europepmc.org/abstract/MED/23951022
http://europepmc.org/abstract/MED/24810493
http://europepmc.org/abstract/MED/23150706
http://europepmc.org/abstract/MED/24346091