Concentration may undergo a variation.Logical formLearned from13 sentences. Biphenyls may undergo concentrations.Logical formLearned from13 sentences. (Trace elements) may undergo concentrations.Logical formLearned from13 sentences. Concentrations can be hourly.Logical formLearned from13 sentences. Concentration can be in international relations.Logical formLearned from13 sentences. Concentration may consist of some courses.Logical formLearned from13 sentences. Concentration can be for students.Logical formLearned from13 sentences. Chemical contaminants may undergo concentrations.Logical formLearned from13 sentences. (Sodium chloride) may undergo concentrations.Logical formLearned from13 sentences. A sense can be constituted-of-or-filled-with concentration.Logical formLearned from13 sentences. Economic activities may undergo concentration.Logical formLearned from13 sentences. Manganese may undergo concentration.Logical formLearned from13 sentences. Concentration can be lower.Logical formLearned from13 sentences. (Air contaminants) may undergo concentrations.Logical formLearned from13 sentences. Changes can be in (calcium concentration).Logical formLearned from13 sentences.