First thing's first - don't ruin your research paper by using "Devil's Horn" as a source. Step one of any paper is evaluating sources - that one evaluates poorly. As far as "Rascher point of view" articles on Ibert, Rascher himself wrote an article on the Ibert in an old issue of The Instrumentalist. I don't remember when the issue exactly was from, but I think it was April 1963. If you can find a copy of the famous radio interview, I think he talks about Ibert in that as well.