A trail can be erratic.Logical formLearned from9 sentences. Persons may blaze a trail.Logical formLearned from9 sentences. (Hiking trails) may pertain-to persons.Logical formLearned from8 sentences. A trail may be divided into some sections.Logical formLearned from8 sentences. Some (hiking trails) can be in an area.Logical formLearned from8 sentences. A trail can be mountainous.Logical formLearned from8 sentences. International standards can be for trails.Logical formLearned from8 sentences. A new standard can be constituted-of-or-filled-with trail.Logical formLearned from8 sentences. Trails can be through a forest.Logical formLearned from8 sentences. Some trails can be constituted-of-or-filled-with difficulty.Logical formLearned from8 sentences. A trail may pertain-to ancients.Logical formLearned from8 sentences. A trail may be marked.Logical formLearned from8 sentences. (Trail systems) can be regional.Logical formLearned from8 sentences. A trail can be geological.Logical formLearned from8 sentences. A trail may follow a path.Logical formLearned from8 sentences.