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Published online by Cambridge University Press: 20 November 2018
This paper is concerned with a question which occurs in [6, p. 346] and uses the notation of that article. Thus K ⊃ K 0 are p-adic fields (p ≠ 2) with residue fields k ⊃ k 0 and having respective rings of integers R ⊃ R 0, G 0 = G 0(K/K 0) is the group of inertial automorphisms of K over K 0,I(K/K 0) is the R module of integral derivations on K over K 0 and Ī(K/K 0) is the k space of derivations on k induced by I(K/K 0). The question here dealt with is the following. Given fields k ⊃ k 0 of characteristic p(≠0, 2) with k/k 0 finitely generated, which subspaces of the k space, Der(k/k 0), of derivations on k over k 0 have the form Ī(K/K 0) for some pair of p-adic fields K ⊃ K 0 having k ⊃ k 0 as residue fields. We note the following connection between Ī(K/K 0) and G 0(K/K 0).