(Surface coal mining operations) may undergo a regulation.Logical formLearned from19 sentences. A (coal production) may pertain-to a nation.Logical formLearned from19 sentences. Persons may need coal.Logical formLearned from19 sentences. A (surface coal mining operation) may be conducted.Logical formLearned from19 sentences. Trade can be in coal.Logical formLearned from19 sentences. Levels can be constituted-of-or-filled-with (coal dust).Logical formLearned from19 sentences. Coal may undergo a formation.Logical formLearned from19 sentences. (Coal prices) can be international.Logical formLearned from19 sentences. A head may pertain-to a (coal mine).Logical formLearned from19 sentences. A coal may undergo a production.Logical formLearned from19 sentences. A (methane explosion) may tear through a (coal mine).Logical formLearned from19 sentences. (Coal deposits) may pertain-to a country.Logical formLearned from19 sentences. A country may have (coal mines).Logical formLearned from19 sentences. A fire may break_out in a (coal mine).Logical formLearned from19 sentences. Some (coal miners) may be killed in an explosion.Logical formLearned from19 sentences.