I am reading a note at Page 63

ftp://ftp.math.ethz.ch/users/pink/FGS/CompleteNotes.pdf

It says whenever G is finite and flat over S the functor Hom(G,H) is representable. But it does not give the proof or any references.

Can anybody help me with this question?

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  [1]: https://i.sstatic.net/eKDQN.jpg