DOC: Update orignal reference for isotype example
Isotype Visualization
=====================
Isotype Visualization shows the distribution of animals across UK and US.
+Inspired by [Only An Ocean Between, 1943](http://www.thomwhite.co.uk/?p=1303). Population Live Stock, p.13.
+This is adapted from Vega-Lite example https://vega.github.io/editor/#/examples/vega-lite/isotype_bar_chart
'''
# category: case studies
import pandas as pd
