middle and small coal mine的用法和樣例：
例句
- Medium and small coal mines in north of Shaanxi Province generally adopt longwall remaining coal pillars support mining.
摘要長壁留煤柱支撐法開採是陝北中小煤礦普遍採用的一種採煤方法。 - Many small and medium-sized coal mine production safety is still not solve the problem, this issue must not be the existence of trusting to luck, said Zhou Dadi.
許多中小煤礦仍然不能解決安全生產問題，在此問題上絕不能存在僥倖心理，周大地說。
