"All of this is contributing to an underground, sort of 'black' economy, which is very difficult for any of us to measure and gauge.

VOA: standard.2010.06.17

and a number of things that are just, sort of, difficult for human beings to process and make intelligent decisions.

还有一系列，人们难以去控制,并且做出正确决定的事情。

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Well, that's pretty difficult. It, you know, I think it's easiest to do that in sort of an informal way.

分配起来确实挺困难的。你知道的，以一种非正式的方式反而更容易做到。

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The anticipatory period leading up to a performance of any sort is difficult for most performers, but there is a particular challenge involved in waiting to perform an act that is to some degree extemporaneous, and battle rap is a rather harrowing mix of the extemporaneous and premeditated.

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And I think it's statements like that and rumors like that that get started, and then from there, of course, it makes it very, very difficult to sort of extract the truth from this web of rumors and suppositions.

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Distribution of that sort has traditionally been more difficult with books, since it is harder to print and disseminate thick wads of paper than it is to burn discs or download video files.

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