© Stringer/AFP/Getty ImagesPresident John F. Kennedy's murderer Lee Harvey Oswald is pictured during a 1963 press conference after his arrest in Dallas.
Don't expect an end to the conspiracy theories about the assassination of President John F. Kennedy - even after the vast network of JFK-obsessed researchers pore over the final trove of government documents.

That's because the thousands of files made public by the National Archives late Thursday - and others that President Donald Trump announced will undergo an additional 180-day review - are still vastly incomplete, according to former government officials and leading assassination scholars, including those who believe Lee Harvey Oswald acted alone and the many more who don't.

They insist that much of what the government knew or suspected about people who may have had knowledge of Kennedy's murder, or who had a motive to take part in a conspiracy or cover-up, remains hidden from the public or was destroyed.

The Secret Service, for example, has acknowledged it destroyed some of its records about the events in Dallas on Nov. 22, 1963. Army and Navy intelligence files on key individuals have never been made available, and in some cases were shielded from a trio of government probes into Kennedy's killing in the 1960s and 1970s.

Also missing, they say, is part of a CIA report on Oswald, an ex-Marine who defected to the Soviet Union before returning to the United States. And much mystery remains about all the files maintained by the late James Jesus Angleton, the top CIA counterintelligence official who took over the agency's probe of the assassination.

"I have no doubt he destroyed files on the initial leads of the investigation," said John Tunheim, who chaired the government's Assassination Records Review Board from 1992 to 1998 and is now a federal judge in Minnesota and had access to all the files in the JFK collection. "It seems inevitable there were other files that were destroyed."

The documents made public and those still undisclosed Thursday represent the last of the paper trail that the CIA, FBI and other agencies provided to Tunheim's special oversight board, which was empowered by Congress to collect anything left in government files that might relate to the plot against Kennedy. Congress passed that law after Oliver Stone's movie JFK called attention to a host of conspiracy theories about the murder.

But officials who investigated the case and researchers who study the assassination point to a number of relevant documents known or believed to have existed that aren't found in the JFK collection.

Evidence for their existence includes the testimony of individuals with direct knowledge, citations in other files, or evidence of meetings and intelligence and law enforcement operations that probably would have been recorded in some fashion.

Tunheim also believes that some documents his review board did not deem relevant to the assassination two decades ago may very well be, given new details that have emerged in the years since.

One such set of suspected files involves a shadowy CIA figure named George Joannides, whom a subsequent Freedom of Information Act lawsuit revealed had possible links to Oswald that he hid from Congress.

Joannides, who died in 1990, served as the CIA's liaison to the House Select Committee on Assassinations, which concluded there were strong indications of a conspiracy. But he had never divulged at the time that he had managed a group of Cuban exiles seeking to overthrow Cuban President Fidel Castro and had ties to Oswald.

Robert Blakey, who was the staff director of the House panel, is still livid at how he and his staff were misled and "the fact that I didn't get to put him under oath."

"We were never able to get the file of the group Lee Harvey Oswald met with," Blakey, now a law professor at Notre Dame University, said in an interview.. "Joannides was the supervisor of that group."

None of the documents released Thursday include any referencing Joannides, a search of the titles and subjects shows.

The legion of researchers obsessed with the assassination - ranging from academics to grass-roots sleuths - are notoriously at odds with each over who killed Kennedy and who may have covered up the evidence, to protect either government secrets or the culprits. The charges and counter-charges of being a kook or a government stooge of one stripe or another are legendary.

But they almost universally agree that the final batch of records will add little if any new information, in large part because some of the most potentially revelatory information simply isn't in there.

For example, they view the scant official record on Oswald as one of the strongest indications that officialdom knew things it never wanted made public.

"It is literally impossible that Lee Harvey Oswald was not all over government records," said Russ Baker, an investigative journalist and founder of the alternative news site WhoWhatWhy.com, which has a team of researchers poring over the newly released documents. "The simple fact there are hardly any reports that mention him is evidence of a cover-up."

Fellow investigative journalist Gerald Posner, who unlike Baker believes Oswald acted alone, agreed that the official record on the assassin almost certainly contains missing pieces. Those could include files that would have shed light on any links Oswald had to the U.S. intelligence community.

"Assume for a second there was something truly, horrifically embarrassing to the CIA or FBI?" Posner posed, such as information suggesting that those agencies might have been able to prevent the assassination. "They left the files in the National Archives? It would be startling to find something in there that blew the case open."

One vanished set of CIA documents on Oswald is the fifth of a seven-volume collection known as his 201 file. It was compiled by the agency's Office of Security.

"There are documents that speak about Volume 5 and people who read it," said John Newman, a political science professor at James Madison University and 20-year veteran of Army intelligence. "Where and when did it go extinct?"

He said he has come across a number of other cases in which files have gone missing, including some he reviewed when the Assassination Records Review Board first released documents in the 1990s.

Some of those gaps Newman attributed to simple bureaucratic mismanagement. Tunheim, the federal judge, also said that in his experience that the CIA's filing system "was not well put together."

But that can't explain it all, Newman insisted. The records that disappeared all seemed to be important, such as testimony to the Senate's Church Committee in the mid-1970s that in the course of probing CIA abuses delved into the Kennedy assassination, he said.

"There was a consistency to the type of information that went missing," Newman said in an interview. "The high number of incidents seem to not be able to be ascribed to human error. We should have screw-ups on things that don't matter."

Some of the most frustrated people are the former government investigators like Blakey, who is also critical of the Secret Service's failure to retain documents.

Dan Hardway, who also was on the staff of the House probe in the late 1970s, believes that the records held in the National Archives are far from complete, and that his panel's work was stymied by the CIA. He recently filed a lawsuit along with Blakey and another former staffer seeking agency files about its relationship with their committee, including anything related to Joannides.

In its response to the lawsuit, the CIA reported that 13 documents exist that are related to Hardway's request - but none have been released and they are not in the National Archives.

Mysteries also abound about numerous files that are not listed among the 3,571 documents identified in the National Archives JFK collection as "withheld in full."

"There are a variety of things we know were torched," said Rex Bradford, president of the Mary Ferrell Foundation, a nonprofit research organization that has digitized hundreds of thousands of documents and government reports about the Kennedy assassination.

For example, Army intelligence informed the House committee that it had destroyed a file on Oswald, said Bradford, a leading authority on the government files that have been released.

"There are references in other files to a 'Harvey Lee Oswald' FBI file no one has ever seen," he added.

The last government attempt to shake loose what is left - the records review board headed by Tunheim - had to rely on agencies being forthcoming. And people who worked for the board have lingering doubts they were able to get their hands on everything.

"We had to rely on the agencies to provide us documents pursuant to requests we made," the board's executive director, David Marwell, said in an interview. "There was no practical way for us to determine if they were completely compliant." The panel was worried enough, he said, that it put agency officials it was working with to find relevant documents under oath.

What is clear is that the final JFK documents will not be the last word.

Said Newman, the former Army intelligence officer: "This thing is not over by a long shot."