During the Killian documents controversy in 2004, the authenticity of the documents themselves was disputed by a variety of individuals and groups. Proof of authenticity is not possible without original documents, and since CBS used only faxed and photocopied duplicates, authentication to professional standards would be impossible regardless of the provenance of the originals. However, proving documents inauthentic does not depend on the availability of originals, and the validity of these photocopied documents has been challenged on a number of grounds,[1][2][3][4][5][6][7][8] ranging from anachronisms in their typography to issues pertaining to their content.