GGU-STABILITY: Centre-points menu (for slip circles only)

• GGU-STABILITY: "Define in quadrilateral" menu item
• GGU-STABILITY: "In rectangle" menu item
• GGU-STABILITY: "Individually (graphically)" menu item
• GGU-STABILITY: "Individually (editor)" menu item
• GGU-STABILITY: "Refine" menu item
• GGU-STABILITY: "Info" menu item
• GGU-STABILITY: "Define search grid" menu item
• GGU-STABILITY: "Semi-automatic" menu item
• GGU-STABILITY: "Delete individually" menu item
• GGU-STABILITY: "Delete all" menu item
• GGU-STABILITY: "Display" menu item