This has been inspired by this MO question: [Harmonic maps into compact Lie groups](https://mathoverflow.net/questions/48174/harmonic-maps-into-compact-lie-groups)


Just for joking: which is your favourite never appeared forthcoming paper?


(do not hesitate to close this question if unappropriate)



Never appeared forthcoming papers
This doesn't exactly count as an unpublished forthcoming paper, but the supposed original proof of Fermat's Last Theorem that was "too large to fit in the margin" should probably be mentioned here.


