Each ring's width is divided by the series' standard deviation
Sx = √Σ(xt-mx)2, mx is mean of series' widths
Each tree has its own Biological Growth Curve
which is subtracted; e.g., exponential yt = ae-bt+k
Combined record shows influence of individual trees
The individual growth curves are subtracted by subtracting a curve fit to the series.
The combined series does not show the influence of individual trees' growth patterns