We obtain a general representation $f(x,y) = φ(u(x) - y)$ for solutions $f : X^2 → Z$  of the differential equation $Df_y(x)(h) + Df^x(y) (Du(h)) = 0,$ where $D$ is the differentiation operator and $u : X → X$  is a differentiable operator of tensor type, in the class of separately differentiable continuous mappings and in the case $X = \mathbb{R}^n$.

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