| More topics under "B28 - Working cement, clay, or stone" (103,421) |
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| B28B - Shaping clay or other ceramic compositions, slag or mixtures containing cementitious material, e.g. plaster (64,825) |
| B28C - Preparing clay; Producing mixtures containing clay or cementitious material, e.g. plaster (14,023) |
| B28D - Working stone or stone-like materials (24,573) |