Tag 'source:ref = extrapolation'

• 38: source:ref
• 35: source
• 25: ref
• 25: power
• 20: design
• 18: structure
• 13: operator
• 13: railway:electricity:ref
• 13: material
• 13: check_date
• 13: railway:electricity
• 9: voltage
• 7: line_attachment
• 4: railway:signal:electricity:type
• 4: railway:signal:electricity
• 4: railway:signal:electricity:form
• 4: railway:electricity:jumpering
• 1: note