I am using the procedure of stratified sampling for variance reduction. In the Glasserman book the algorithm for stratified the terminal value of the Brownian motion is given for european options. For asian options he has written to stratify the average of brownian motions : $ W(t_1), W(t_2) ... W(t_m) $
But i cannot figure out how to exactly go about doing this. Any resource for this specific problem would be highly helpful.