I'm sure there is a very simple answer to this question, but I couldn't find it on the board or in the 3dregana help. I am running some whole-brain individual differences analyses (hold the voodoo), and need to control for two other variables. I'd also like to look at the effects of the control variables. My question is what do I put in the model flag? Is there another help file (other than 3dregana) that explains this in more detail with examples?

My command looks something like this

3dRegAna \
-rows 72 \
-cols 3 \
-xydata 2.1 3.6 25 ../${subject1}/${regcoeff} \
-xydata 2.7 2.1 32 ../${subject2}/${regcoeff} \
-xydata 1.6 3.1 31 ../${subject3}/${regcoeff} \
.
.
.
-model [what should I put here to see all three effects in my output files?]

Thank you all!