interestingly, this boy's work was allegedly confiscated by the FBI when he died. there is a museum of his work in belgrade, but some of his papers are alleged to be classified to this day. imagine being afraid of nearly 100 year old notes.
dynamic theory of gravity
it would be interesting to submit a FOIA request for these documents to confirm these allegations. some sources claim that these papers are still heavily redacted to this day.
apparently, tesla had some issues with einstein's theory of relativity. he never published his own theory and his notes on the topic are allegedly still classified.
Tesla's Dynamic Theory of Gravity
both tesla and marconi allegedly claimed to have contact with aliens while developing radio communications technology.