[word=validity] [lemma=of] [tag=DT] [tag=NN] [lemma=□]
[word=validity] [lemma=of] [tag=DT] [tag=NN] [lemma=claim]
[word=validity] [lemma=of] [tag=DT] [tag=NN] [lemma=of]
Central to the administration of this system is the issuance of certificates of registration , which are legal documents providing evidence of the validity of the copyright claim and the underlying facts .