On: "You Don't Understand Ordinary People" - Feynman Gives Advice to Wolfram

[functional-tree]

What does the "RPF;ht" at the bottom stand for? (I vaguely recall this being an old convention of something?)

[kscaldef → functional-tree]

'ht' is Helen Tuck, the secretary at Caltech's Theory Group for many years; that mark indicates she typed the letter. I was there many years after Feynman passed away, but I have fond memories of Helen and some of the stories she had to tell about the "old days".

[mturmon → kscaldef]

http://pr.caltech.edu/periodicals/336/articles/Volume%202/05...

[apowell → functional-tree]

They're the initials of the author (in caps) and the typist (in lowercase).