و آر ایل:https://www.researchgate.net/profile/Mark_Smethurst/publication/301546802/figure/download/fig13/AS:668455724408840@1536383672737/Left-Portion-of-the-eU-grid-data-set-of-Fig-3-coloured-according-to-the-eU-intervals.png
و آر ایل:https://www.researchgate.net/figure/Left-Portion-of-the-eU-grid-data-set-of-Fig-3-coloured-according-to-the-eU-intervals_fig13_301546802
