Frank Arey, former deputy director of the Arkansas Heritage Commission (and, thus, former boss of our good friend Mark Christ), gave an excellent paper on Poison Springs at the annual Arkansas Civil War Symposium in Little Rock. I'm not remembering the date, but it was the same year Frank resigned to go back into private practice. I think the paper was included in one of the publications that resulted from the symposium series. (While his paper didn't concentrate on the Choctaw, but rather looked at the massacre's causes, it still had several source references you might find useful.)