[gsinclair]

They were once coming in English-language publications but now are seen in only The New Yorker, The Economist, and one other. Can anyone recall which?

[eru]

Interestingly, they seem to survive most in naïve than in words like coöperate.

Co-operate is much more common than na-ive (which I've never seen). But both cooperate and naive seem reasonably well accepted.