Kosara R. An Empire Built On Sand: Reexamining What We Think We Know About Visualization [pdf file]
Data Visualization (definitions)
Data Visualization for Human Perception – Few, Stephen (2014): Data Visualization for Human Perception. In: Soegaard, Mads and Dam, Rikke Friis (eds.). « The Encyclopedia of Human-Computer Interaction, 2nd Ed. ». Aarhus, Denmark: The Interaction Design Foundation.
William S Cleveland and Robert McGill. Graphical Perception: Theory, Experimentation, and Application to the Development of Graphical Methods. Journal of the American Statistical Association. Vol 79 No 387, (Sept 1984), 531-554 Available online.
Color Hex Color Codes – Color-hex gives information about colors including color models (RGB,HSL,HSV and CMYK), Triadic colors, monochromatic colors and analogous colors calculated in color page. Useful tool for selecting color palettes for a visualization.
The Noun Project – Icons and symbols to communicate words in a visual language. Impresive collection of well designed icons.
FlatIcon – A lot of free icons. Multiple formats & sizes.
BrainyIcons – Brainy Icons Free is a set of 36 hand-drawn free education icons. The icons are available as AI, EPS, PSD and PNG (in 4 sizes: 32×32, 48×48, 64×64, 128×128) and released under the Creative Commons Attribution license.