Cob: Rammed Earth floor

[Jonathan Smith]

Hello.  I'm working on building a small earth oven and an adjoining shed
that will provide a roof for the oven and enclosed space to do final prep on 
the loaves.  I saw an article in BackHome magazine a couple of years ago about
rammed earth floors - basically a mixture of clay-containing soil, an
aggregate (gravel), lime and/or concrete, and possibly some straw that is
tamped down and 
then coated with boiled linseed oil.  Unfortunately I can't find the magazine 
with the article in it.  Does anybody know of any websites that would have
the information on how to prepare a floor such as this?  The soil is rougly
50% clay
and 50% silt - I need to know how much (if any) additional material needs
to be added.  Thanks for any information.