Study on contrastive outcomes?

[Mike Cahill]

Does anyone know of a study of the sociolinguistic situation of two different languages, one viable and the other endangered, where the two language situations have nearly identical external pressures on both speech communities, yet their language viability outcomes are quite different? The languages would probably be in the same geographical area. I've got a candidate case, and was wondering how unique this might be in the literature.

Mike Cahill