dial books

[Chris.Breckpot]

          Hello, my name is Christian Breckpot, I live in Belgium and I
          recently subscribed to this list.
          I  have a question about dial books.  I own a copy of -Sundials -
          Their theory and construction- written by AE Waugh.  Can somebody
          tell  me  in what respect the books of RJ Rohr and RN & MW Mayall
          differ from Waugh
,s ?
          Best greetings,

          Christian