 We have also proved its existence under strong condition ( in the so called \emph{symmetric case ) highlighting in conclusion some interesting applications in finance and future researches .
<clarity>  We have also proved its existence under strong condition ( in the so called \emph{symmetric case ) highlighting in conclusion some interesting applications in finance and future researches .
 We have also proved its existence under strong condition ( in the so called \emph{symmetric case symmetric case .