english: I did a little bit of research on this for a talk I had to give a few years ago.
non_english: ➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡. ➡➡➡. ➡➡➡➡➡➡➡➡➡➡. ➡➡➡➡➡➡➡➡➡➡. ➡➡➡. ➡➡➡➡➡➡➡➡➡➡. ➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡. ➡➡➡➡➡➡➡➡➡. ➡➡➡➡➡➡➡➡➡➡➡. ➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡➡