the book i have is the illustrated history of sunbeam motorcycles.which includes bicycles.and there are many pictures of george dance from side valves up to testing the overhead cam crossflow s7.the quick one,too quick for the rear axle.so they didnt use it. I havent seen the other book.there is a line up of the 1920 sunbeam riders including dance but not with race numbers although the registration numbers are seen.he was only leading by over 3 minutes ! when an inlet valve broke. i have ridden/owned most bikes but i would still be happiest with a sunbeam.