Previous studies pointed to abnormal blood vessel growth that starves a developing placenta of oxygen, but researchers had little clue what set off those changes.

此前研究指出异常的血管生长使得发育中的胎盘缺氧，但研究者对引发其变化的原因找不到丝毫线索。

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Previous radiation experiments on animals may give a clue for the increase in male births.

舍布博士称，先前在动物身上进行的核放射性实验也许会为男婴出生率的增高提供一些线索。

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On the basis of the history of the woodblock edition summarized by the predecessors, this dissertation initially put forward a more complicated clue and fills the vacant area in the previous research.

在前人总结的版刻演进纵向线索的基础上，初步贯穿起另一条纵横交错、层次更为复杂的线索，并补充了已有研究中某些时间段的空白点。

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Admittedly, at this point, the ratio was not very high with respect to previous peaks, which might provide a clue as to why the ensuing correction was more modest than prior pullbacks.

FORBES: Four Short-Term Risks To The Bullish Case