However, given the high uncertainty margins for the maternal mortality ratio, determining whether there is any real decline at all is difficult (2).

但是由于孕产妇死亡率也存在很高的不确定性，所以很难阐明是否真正有所降低[2]。

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The purpose of the present paper is using the nonlinearization approach to study the explicit finite-parameter solution to the difficult (2+1) dimensional soliton equation.

本文主要是用非线性化方法来研究困难的（2+1）维孤子方程的显式的有限参数解的。

youdao

However, working out the precise effects of Basel 2 is difficult.

ECONOMIST: Bothersome Basel

The Ramblers' Association said it would become more difficult to maintain the county's 2, 000 miles of footpaths.

BBC: Sussex countryside budget 'cut to the bone'

In case some politicians found it difficult to understand all this, Article 2(4) spelled it out in unequivocal terms: "All Members shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state".

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