Source: https://www.researchgate.net/profile/Sidonie-Christophe/publication/232959960_Generalisation_symbol_specification_and_map_evaluation_Feedback_from_research_done_at_COGIT_laboratory_IGN_France/links/57a4816d08ae455e8538688d/Generalisation-symbol-specification-and-map-evaluation-Feedback-from-research-done-at-COGIT-laboratory-IGN-France.pdf