From the PRL archives:

It was also a concept that grabbed my mind, ran off with it, and only returned it after substantial renovation and expansion. — Continuations by Alan Nall, Indiana University, 1983

I first encountered this essay on continuations in a green folder in the PRL. It turns out, the author spent a semester at Indiana University working on the same fringe problem for a graduate-level programming languages course. According to the instructor: “What he said was true. He could not stop thinking about the problem the entire semester.” This essay was a kind of final exam.