This new article by Bob Herbst is available at http://unblinkingeye.com/Articles/Azo3/azo3.html. Herbst ran some tests at Dan Smith's request to see how the tonal range of Azo compared with that of platinum/palladium prints, using the test negatives he made for his article on The Effects of Pyro Stain (at http://unblinkingeye.com/Articles/Pyro/pyro.html).