Takeuchi's On coverings and hyperalgebras of affine algebraic groups references Tangent coalgebras and hyperalgebras. I and II, with II being listed as submitted to MAMS. On coverings and hyperalgebras of affine algebraic groups. II also cites both papers, now with II listed as 'to appear'. On coverings and hyperalgebras of affine algebraic groups. III does not mention "Tangent coalgebras and hyperalgebras. II" at all.
This could usually indicate a planned paper that was never written (indeed, I checked Never appeared forthcoming papers to see if it was mentioned there), but On coverings and hyperalgebras of affine algebraic groups cites results from "Tangent coalgebras and hyperalgebras. II" by number, and, again, it is listed there as submitted, leading me to believe that it was actually written. Does the paper exist under some other name? Was it withdrawn due to an error?
