“…We identified 11 techniques that use only color to visualize group membership explicitly [Dek01, DS13, DYL*15, DYLL15, IMMS09, LWC*14, NIST12, SGKS15, SKL*14, TLTC05, vHW08]. Nodes that belong to only one group are simply colored with respect to that group [DS13, DYL*15, DYLL15, SGKS15, SKL*14, vHW08] (Figure a). For flat overlapping groups , nodes are represented using glyphs—‘graphical objects designed to convey multiple data values' [War04].…”