 In 1887, Cesàro came close to stating the definition of (C, "n") summation, but he gave only a few examples.In particular, he summed to by a method that may be rephrased as (C, "n") but was not justified as such at the time.He formally defined the (C, n) methods in 1890 in order to state his theorem that the Cauchy product of a (C, "n")-summable series and a (C, "m")-summable series is (C, "m" + "n" + 1)-summable.