An obstacle can be impenetrable.Logical formLearned from10 sentences. Obstacles may be created by a country.Logical formLearned from10 sentences. Obstacles can be increased.Logical formLearned from10 sentences. Obstacles can be to an accord.Logical formLearned from10 sentences. Obstacles can be in work.Logical formLearned from9 sentences. An obstacle can be to ratification.Logical formLearned from9 sentences. Obstacles can be to an economic development.Logical formLearned from9 sentences. Obstacles can be to an adoption.Logical formLearned from9 sentences. Obstacles can be to elections.Logical formLearned from9 sentences. An obstacle can be invisible.Logical formLearned from9 sentences. Differences can be an obstacle.Logical formLearned from9 sentences. Violence can be an obstacle.Logical formLearned from9 sentences. Obstacles may block progress.Logical formLearned from9 sentences. Obstacles can be to co-operation.Logical formLearned from9 sentences. Obstacles can be to peace.Logical formLearned from9 sentences.