 A distribution may also be multiplied by a rapidly decreasing infinitely differentiable function to get another distribution, but 
it is not possible to define a product of general distributions that extends the usual pointwise product of functions and has the same algebraic properties.This result was shown by , and is usually referred to as the 
"Schwartz Impossibility Theorem".It is desirable to choose a definition for the derivative of a distribution which, at least for distributions derived from smooth functions, has the property that formula_13.