Speed and reliability in travel search, especially around flights, is an extremely difficult area to master.

旅游搜索的速度和可靠性最难掌控，尤其是对于机票搜索。

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This can be especially difficult for people who are not able to easily walk to a different flight's waiting area.

对于一些行走不便的旅客来说走到另一架飞机的候机室是非常困难的。

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The support structure during the excavating of deep foundation pit is difficult, especially in the dense buildings, high groundwater level and thick soft soil area.

深基坑开挖支护是基坑施工的重点，尤其是在建筑密集、地下水位高、厚软土地区的深基坑支护，更是工程界关注的难题。

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The new study, published online in the journal Nature Biotechnology, represents an early example of how social networking could play a role in clinical trials, an area of medical science with strict procedures that many would consider especially difficult to apply in the online world.

WSJ: ALS Study Falls Short, But Use of Social Media Holds Promise

Investors seem to be more comfortable selling EUR rallies at the moment, especially since the single currency is finding it difficult to stride away from the psychological 1.30 area.

FORBES: Currency Traders Await Central Bank Clues