Books by Hampton Sides

That is from Hampton Sides's quite interesting Blood and Thunder: The Epic Story of Kit Carson and the Conquest of the American West .  From the specialized academic literature, here is an entire study of the mother-in-law taboo (JSTOR) ; I'm not sure any of the offered hypotheses or explanations are persuasive.  It seems the taboo lasted well through the twentieth century.  Here is another discussion , under the more general heading of Navajo taboos: