Others have also recognized this phenomenon, and different types of "Cultural Units" have been described. Garreau, in his book, “The Nine Nations of North America” defines what he considers a Human Geographic Unit at this higher level of the progression quite well:

“Consider...the way North America really works. It is Nine Nations. Each has its capital and its distinctive web of power and influence. A few are allies, but many are adversaries. Several have readily acknowledged national poets, and many have characteristic dialects and mannerisms. Some are close to being raw frontiers; others have four centuries of history. Each has a peculiar economy; each commands a certain emotional allegiance from its citizens. These nations look different, feel different, and sound different from each other, and few of their boundaries match the political lines drawn on current maps.”

Cultural Resource Units aggregate to form Global Resource Units in the Natural Borders mapping system.