Created by Nikhil VJ in QGIS using Georeferencer plugin and keeping a snap setting on. Another browser-based method is shared here: http://datameet.org/2016/08/12/guide-on-digitizing-static-maps/
See a composite map featuring this dataset superimposed with the previous boundaries, here: https://nikhilvj.carto.com/viz/718f58d8-8e07-11e6-8015-0e3ff518bd15/embed_map
Disclaimer: These boundaries have been manually traced over low-res image/pdf maps. Inaccuracy is inevitable. Use with your own wisdom. If you find an error, kindly fork, correct and share link / pull request of corrected map. Or comment here.
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This work is shared under a Creative Commons BY-NC-SA 4.0 license.