But Howard-Yana Shapiro, head of plant science and external research at Mars, thinks that science could greatly increase the yield.

VOA: special.2010.10.19

There is a lot of research showing how difficult it is to change happiness based on external factors.

很多研究表明,基于外在因素改变快乐很难。

哈佛公开课 - 幸福课课程节选