Complex sentence: As a potential primary source, the content of the released VENONA papers is essentially unverifiable and some are skeptical of both the substance and the prevailing interpretations made since the release of the VENONA material.
Split into simpler sentences: As a potential primary source, the content of the released VENONA papers is essentially unverifiable. Some are skeptical of both the substance and the prevailing interpretations made since the release of the VENONA material.