Five decades after President John F. Kennedy was fatally shot and long after official inquiries ended, thousands of pages of investigative documents remain withheld from public view. The contents of these files are partially known - and intriguing - and conspiracy buffs are not the only ones seeking to open them for a closer look. Some serious researchers believe the off-limits files could shed valuable new light on nagging mysteries of the assassination - including what U.S. intelligence agencies knew about accused assassin Lee Harvey Oswald before Nov. 22, 1963. It turns out that several hundred of the still-classified pages concern a deceased CIA agent, George Joannides, whose activities just before the assassination and, fascinatingly, during a government investigation years later, have tantalized researchers for years. This is not about conspiracy, this is about transparency," said Jefferson Morley, a former Washington Post reporter and author embroiled in a decade-long lawsuit against the CIA, seeking release of the closed documents. "I think the CIA should obey the law. I don't think most people think that's a crazy idea." But so far, the Joannides files and thousands more pages primarily from the CIA remain off-limits at a National Archives center in College Park, Md. Anthony Summers, a British author whose sequel to his JFK book Not In Your Lifetime will be released this year, [said] "By withholding Joannides material, the agency continues to encourage the public to believe they're covering up something more sinister."