On Sun, 9 Nov 2008 19:30 Ashley Moran wrote: >Hi Keith > >I flagged this thread in case anyone replied, but sadly no-one did. >Were you able to find an answer? > >If not, I saw a book years ago in a shop called the Fats of Life[1] >which maybe can tell you. I haven't read it, though. > >Ashley > >[1] http://www.amazon.co.uk/Fats-Life-Caroline-M-Pond/dp/0521635772 Still looking for an answer for non-scientists, Ashley. Thanks for the tip. I ordered the book as soon as I read your reply. Keith