专家们早就认识到，这个令人沮丧的问题是由多种原因造成的。
Experts have long recognized that this discouraging problem has multiple causes.
这种情况是由多种原因造成的，但其中自有图书馆工作不充分的原因。
That is caused by many factors among which is inadequate library work.
结果表明，氨水储槽的泄漏由多种原因造成，残余应力过大是主要因素。
It was conduded that large residual stress was the main cause of ammonia leakage.
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