just to make it more difficult for them to operate. Shaaf also says that the government has been using whatever laws it can to shut down organizations dedicated to civic activism.

VOA: standard.2009.08.04

Now the intervention studies are stronger methods than the epidemiology studies but they're also more difficult studies to do.

相比传染病学研究,干预性研究更有效,但也更难执行

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选

The 60-vote advantage is also important because it will make it far more difficult for Republicans to block passage of bills through a filibuster, in which senators tie up the floor in long speeches to prevent a vote.

VOA: standard.2009.06.30

And,this constant movement of population also affects the humanitarian workers as it makes the planning and the delivery of aid much more difficult because we cannot predict where the people are going or if they are coming back."

VOA: standard.2009.06.21