In addition, the covering was strengthened by use of such materials as fine earth and straw bag, and the length and quality of stemming were guaranteed, controlling the flying rocks effectively.

此外，采用细土、草袋等材料加强覆盖，保证堵塞长度和堵塞质量，有效地控制了飞石。

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The Dutch controls, stemming from European Union legislation that requires a permit to be issued for the export of dual-use materials, remain in force.

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