re: Brodermund 1904 ref. cited by Rex. You might want to check the date Ehret first mentioned his formula (and I don't know what that date is). Ehret first wrote in the late 1800's and his formula MAY have predated Brodermund. I will let those who can cite specific dates for Ehret's writings, settle this issue. (To me it is not very interesting - whether he derived the formula by himself, or copied it from Brodermund, Ehret was an extremist who put dogma ahead of health, and (in my opinion) a lunatic as well. I say that as a former Ehret follower.) Tom Billings