Editing Total variation (section)

==Historical note==
The concept of total variation for functions of one real variable was first introduced by [[Camille Jordan]] in the paper {{Harv|Jordan|1881}}.<ref>According to {{Harvtxt|Golubov|Vitushkin|2001}}.</ref> He used the new concept in order to prove a convergence theorem for [[Fourier series]] of [[discontinuous function|discontinuous]] [[periodic function]]s whose variation is [[Bounded variation|bounded]]. The extension of the concept to functions of more than one variable however is not simple for various reasons.