There are many unsolved problems in mathematics. Some prominent outstanding unsolved problems (as well as some which are not necessarily so well known) include 1. The Goldbach conjecture .
Buffaloing buffalo Buffaloing buffalo All right, I know, in the previous post I claimed that there were "a very few peculiar exceptions" to my claim that for any arbitrary string of words, with repetitions or without, nearly all orders you can put them in are ungrammatical; and I didn't say what the exceptions were. I can tell (no need to email me) that you, as a curious Language Log reader, want to know.