A remark on differentiable functions with partial derivatives in Lp

We consider a definition of p, δ-variation for real functions of several variables which givesinformation on the differentiability almost everywhere and the absolute integrability of its partial derivatives on a measurable set. This definition of p, δ-variation extends the definition of n-variation of Malý and the definition of p-variation of Bongiorno. We conclude with a result of change of variables based on coarea formula.