"We do not know the true value of our moments until they have undergone the test of memory".
         Georges Duhamel (1884-1966); French novelist. (来源：英语杂志 http://www.EnglishCN.com)

    "Doubt must be no more than vigilance, otherwise it can become dangerous".
         G. C. Lichtenberg (1742-99), German physicist, philosopher.