I listed a number of classic papers on functional languages. I read these papers whenever I have spare time to refresh my mind.

[0] Can Programming Be Liberated from the von Neumann Style? A Functional Style and Its Algebra of Programs

[1] Why Functional Programming Matters, John Hughes, The University, Glasgow

[2] A tutorial on the universality and expressiveness of fold, GRAHAM HUTTON, University of Nottingham, Nottingham, UK

[3] Monads for functional programming, Philip Wadler, University of Glasgow

[4] Theorems for free, Philip Wadler, University of Glasgow

I will keep updating the list of papers here. If you think I missed an important paper, please let me know.