If there is one lesson of the past 46 years, it is to be dubious of that claim.

如果需要对过去46年进行一个经验教训的总结的话，那就是需要质疑过去。

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They consider the plan to be of dubious benefit to most families.

他们认为这项计划对大多数家庭不一定有好处。

《牛津词典》

Animal studies can sometimes be of dubious scientific value, since different species react differently to the same procedure.

动物研究的科学价值有时值得怀疑，因为不同物种对同一操作有着不同的反应。

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Despite these compelling investment considerations, many investors seem to be dubious of considering additional investments in gold.

FORBES: What Will Influence The Price Of Gold In 2013?

Some suspect that its opposition stems from the fear that many expensive and profitable pills would be found to be of dubious value.

ECONOMIST: Developing new drugs

The real action now is in branded generics, which command a premium in many emerging markets due in part to the fear that unknown products might be fake or of dubious quality.

ECONOMIST: Big drug firms embrace generics