Complex sentence: Some critics claim as a potential primary source, the content of the released VENONA papers is unverifiable; nontheless, research from Soviet Archives has added to the corroboration of many identities of cryptonyms in Venona materials.
Split into simpler sentences: Some critics claim that the content of the released VENONA papers is unverifiable. Nonetheless, research in Soviet Archives has added to the corroboration of many identities of cryptonyms in Venona materials.