Authenticity backed on Bush documents. After CBS News on Wednesday trumpeted newly discovered documents that referred to a 1973 effort to ''sugar coat" President Bush's service record in the Texas Air National Guard, the network almost immediately faced charges that the documents were forgeries, with typography that was not available on typewriters used at that time. But specialists interviewed by the Globe and some other news organizations say the specialized characters used in the documents, and the type format, were common to electric typewriters in wide use in the early 1970s, when Bush was a first lieutenant.