The US government has released 2,800 previously classified files on the assassination of President John F Kennedy in 1963.
President Donald Trump said the public deserved to be "fully informed" about the event, which has been the subject of numerous conspiracy theories.
But some documents have been withheld at the request of government agencies.
One memo revealed that the FBI had warned police of a death threat against the assassin Lee Harvey Oswald.
"We at once notified the chief of police and he assured us Oswald would be given sufficient protection", writes the FBI director J Edgar Hoover.
Oswald, a former Marine and self-proclaimed Marxist, was shot dead in the basement of the Dallas Police department two days after President Kennedy was killed.
s the documents are pored over and analysed, other findings include a CIA memo that suggests Oswald spoke with a KGB officer at the Russian embassy in Mexico City. The memo says the KGB officer Oswald spoke with worked for a department "responsible for sabotage and assassination".
Another memo showed that Soviet officials feared an "irresponsible general" would launch a missile at the USSR in the wake of President Kennedy's death.
One memo tells how a British regional newspaper, the Cambridge News, received an anonymous call about "some big news" in the US, minutes before the assassination.
A copy of the memo was released by the National Archives in the US in July, but had gone unreported.
Credit:bbc.co.uk