Sparklines are word-like graphics that have an intensity of visual distinctions comparable to words or letters (Tufte 2006, p. 4).
Byers, J. "Sparkline PHP Graphing Library." http://sparkline.org/.
Tufte, E. Beautiful Evidence. Graphics Press, 2006.
Tufte, E. "Sparklines-Revised Chapter for Beautiful Evidence." http://www.edwardtufte.com/notes-sketches/?msg_id=0001OR&topic_id=1.
