U-2 fuels ?

A friend helped fly drums of some special fuel into Pakistan for Gary
Power's ill fated flight. Google turns up dozens of references for various
special fuels for high-altitude flight, and experimental fuels that didn't
make the cut. But, I could not narrow it down to exactly what was being used
then. The friend, a retired USAF Navigator asked me to check it out. There
is so much information that it is bewildering. Anybody have a good, reliable
online source?
Old Chief Lynn