corroboration

kəˌrɒbəˈreɪʃ(ə)n

noun

evidence which confirms or supports a statement, theory, or finding; confirmation.

there is no independent corroboration for this

confirmation,verification,attestation,affirmation,ratification,endorsement,accreditation,authentication,validation,certification,documentation,evidence,proof,substantiation,support,backing,bolstering,reinforcement,weight