"The original idea for Stockbridge at Christmas was actually conceived in 1956,'57 when Hallmark card corresponds with Rockwell on the idea of an image of an American main street which will symbolize Christmas in America,"

VOA: standard.2009.12.25

Second thing, we started talking about the periodic table and I believe that it's a hallmark of any educated person in the 21st century who is technically literate to know the periodic table by heart.

第二点，我们之前讨论过元素周期表,我相信这是个标志性的特征,对于那些在21世纪里,用心去学习,元素周期表的人来说。

麻省理工公开课 - 固态化学导论课程节选