An (ozone layer) may pertain-to persons.Logical formLearned from78 sentences. An ozone can be low-level.Logical formLearned from73 sentences. Ozone may undergo a distribution.Logical formLearned from71 sentences. An (ozone hole) may undergo a discovery.Logical formLearned from71 sentences. Ozone may undergo measurements.Logical formLearned from68 sentences. Standards can be for ozone.Logical formLearned from68 sentences. An ozone can be high.Logical formLearned from67 sentences. An (ozone layer) may thin.Logical formLearned from67 sentences. Holes can be in an (ozone layer).Logical formLearned from66 sentences. Ozone may undergo a use.Logical formLearned from65 sentences. A hole can be in an ozone.Logical formLearned from57 sentences. Ozone can be in a troposphere.Logical formLearned from56 sentences. An (ozone layer) can be over a continent.Logical formLearned from56 sentences. (Ozone levels) can be elevated.Logical formLearned from53 sentences. (Ozone concentrations) can be high.Logical formLearned from52 sentences.