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            e consider the original
               SDE  and a perturbed
               SDE  We introduce the
               difference  The difference  is given by the following
               SDE  We assume that the functions  and  are such that the solution of the original SDE  changes slightly when the perturbation of the initial condition is slight.
               Hence, the  is small if  is small.
               Consequently,  We substitute these approximations into the SDE for    and note that such SDE scales with the magnitude of  .
               We introduce the process  :  We arrive to the following system of
               SDEs:  The derivative of interest may be expressed in terms of  and  :   |