Therefore the only skills worth formally vouching for are those that require substantial effort to learn .

因此值得做正规 证明的技能，是那些需要花费大量精力去学习才能获得的技能。

They can buy in bulk through Alibaba which acts as a trusted third party vouching for the transaction .

他们可以通过阿里巴巴进行批量购买所 需 产品， 阿里巴巴则作为受信任的第三方对交易的 顺利 完成 提供 保障。

These are references vouching for his ability .

这些都是证明他能力的 介绍 信。

They used to see themselves as vouching for their product as acting as a gatekeeper to the capital markets and providing a valuable social role .

过去，他们认为自己 要为产品 担保，作为“资本市场的看门人”，扮演有价值的社会角色。