These are just essays, so there's not much space to go into the breadth of differences between Native cultures, other than to point out that those differences are big enough that one can't, and shouldn't, gloss over them. Tol Foster, as I understand him, would go on to say that the breadth of differences is one of the reasons that Native lit-crit should avail itself of regional perspectives. Daniel Heath Justice illustrates the importance of that breadth in his discussion of how the differences between Oglala and Pequot experience and history lead to a situation where Delphine Redshirt was claiming that the Pequot weren't "real" Indians. In both cases, the authors are discussing issues and strategies for approaching works by Native authors; neither are even attempting to lay out all the knowledge that one would need to be able to apply those strategies.