If f(x), g(x) and h(x) be three differentiable functions, then the product rule for these three functions can be written as:
D[f(x). g(x). h(x)] = {g(x). h(x)} * D[f(x)] + {f(x). h(x)} * D[g(x)] + {f(x). g(x)} * D[h(x)]