They reported that clouds are an important and heretofore uninvestigated contributor to the climate.他们报告说, 云是影响气候的一个重要但尚未做 过研究的因素。

The irony of getting her chance to work in a less stimulating environment than heretofore did not escape her.让她有机会到一个迄今为止最无趣的环境工作, 这种让人哭笑不得的状况她不是不知道。