Not sure if this was addressed to me, but in case it was: I actually did my Ph.D. thesis on double-barred galaxies, and have continued to work on and off on barred galaxies over the years; here's a partial list of paper's I (Peter Erwin) have authored or co-authored on the subject: https://ui.adsabs.harvard.edu/search/fq=%7B!type%3Daqp%20v%3...