On 28 May 2010 19:07, mike cook <mike.cook at orange.fr> wrote: > This I think > http://www.allanstime.com/Publications/DWA/Science_Timekeeping/TheScienceOfTimekeeping.pdf Thanks for the link Mike. Steve -- Steve Rooke - ZL3TUV & G8KVD A man with one clock knows what time it is; A man with two clocks is never quite sure.