References/Notes/Attributions:
Source
M. Friendly (2000), Visualizing Categorical Data, pages 20–21.
References
K. Pearson (1900), On the criterion that a given system of deviations from the probable in the case of a correlated system of variables is such that it can be reasonably supposed to have arisen by random sampling, Philosophical Magazine, 50 (5th series), 157–175.
M. Friendly (2000), Visualizing Categorical Data. SAS Institute, Cary, NC.