How enterprises use functional languages, and why they don’t [pdf]

The author of the linked paper, Philip Wadler, is just phenomenal.

http://homepages.inf.ed.ac.uk/wadler/

>"I was a principal designer of Haskell. With Simon Marlow, I developed a type tool for Erlang. I am a founding member of IFIP WG 2.8 Functional Programming, and served as editor-in-chief of the Journal of Functional Programming."