Create data based on the Gleditsch & Ward (G&W) or Correlates of War (COW) state system memberships lists. This is useful as a template for merging other sources of data that have conflicting sets of states.
See static docs at https://andybeger.com/states and the source code at https://www.github.com/andybega/states
Gleditsch, Kristian S. & Michael D. Ward. 1999. ``Interstate System
Membership: A Revised List of the Independent States since 1816.''
International Interactions 25: 393-413.
Correlates of War Project. 2017. ``State System Membership List, v2016.''
Online, http://correlatesofwar.org