They were made of bronze, bone, tooth and "Mud Cover" (picture 6), etc.

印材有铜印、骨印、牙印、陶印以及泥封（图六）等。

youdao

The technology was helped by the density of houses and other buildings, made of mud brick so that they showed up somewhat clearly against the looser soil cover.

这种技术利用了显现房屋和其他由泥砖建成的建筑的密度特性，因此可以清晰的显现被松散的泥土覆盖的物体。

youdao

After sitting down again, he looked at the book. It was old, the cover was torn, and the pages were stained with mud and water.

再次坐下之后，他看着这本书，有点旧了，封皮已经破损了，书页也沾着泥水。

youdao

Troops moved forward block by block, hunting for cover behind crumbling mud-brick walls and houses.

CNN: 's Karl Penhaul

Hills that offer cool respite have lost significant green cover to overzealous building, leading to mud slides and, recently, flash floods.

CNN: Georgetown