APBRmetrics

In Appendix 4 of Dean Oliver's book "Basketball on Paper", an approach to estimate turnovers and offensive rebounds in the NBA prior to 1974 using multivariate regression analysis is presented. I understand the approach but I am stumped about what the acronym "Seas" means. Oliver does not define it. The other acronyms in the formulas (e.g., G, FGA, FTA, REB, PF, DQ, FGM, FTM, PTS, and AST) are obviously basketball statistics. Any help would be much appreciated.

Season

Thanks, Mike.

Let us know how this goes. Better yet, let the folks at b-r.com know, as it might fill in some blanks in the past.
I've made a few passes at it, with pretty high uncertainty. But I don't think I've tried Season as an actual variable.