First the thesis discusses the concepts of forest certification and holds that the forest certification concepts are different for various certification systems.

本文首先讨论了森林认证的概念问题，提出不同体系的森林认证的概念是有区别的。

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Countless certification systems from around the world help travelers determine which providers are committed to environmental and social sustainability.

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More detailed rating systems and independent certification could help. eLance already gets buyers to evaluate sellers in several categories, such as timeliness and responsiveness.

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The review includes not just the 787's ground-breaking lithium-ion battery system, but how that system works with the aircraft's electronic systems, their certification, manufacture and assembly, he said.

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