the ox, oy, oz things seems to be booleans which are here to "activate" a
derivative operator.
ox=%T, oy=%F, oz = %T
then the expression is:
2
d
dfp(i) = ----- s (xp(i),yp(i),zp(i))
dx.dz
I will try to find a good way to present this while I am converting text
equations into mml.
YC