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regular pen for writing system 'sphere' with internal ink and paint with special instruments and devices that allow the tracking of curves, circles or circles.or curvilinei pathways as a normal compass, by what principle the flexibility of reservoir containing ink
regular pen for writing system 'sphere' with internal ink and paint with special instruments and devices that allow the tracking of curves, circles or circles.or curvilinei pathways as a normal compass, by what principle the flexibility of reservoir containing ink