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而是实际的书籍，比如有关防御工事的，水力学，炮术，航海和造船的。
It was practical books about fortifications, hydraulics, artillery, navigation, and shipbuilding.
youdao
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而是实际的书籍，比如有关防御工事的，水力学，炮术，航海和造船的。
It was practical books about fortifications, hydraulics, artillery, navigation, and shipbuilding.
youdao