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http://europepmc.org/abstract/MED/21157497
http://europepmc.org/abstract/MED/28481359
http://europepmc.org/abstract/MED/28218421
http://europepmc.org/abstract/MED/24211491
http://europepmc.org/abstract/MED/28577310
http://europepmc.org/abstract/MED/7704014
http://europepmc.org/abstract/MED/26648449