I am new to STATA and working on repeated cross-sectional data for Difference-in-Difference analysis. I have treatment and control groups before and after the intervention. My treatment and control groups are, however, unbalanced (the covariates are significantly different across the two groups both in pre-and post-intervention). I, therefore, want to apply the matching technique to match the three groups (pre-treatment, pre-control, post-control) to my post-treatment group and then use DID. Any guidance about the STATA commands and references to papers that have applied this technique would be helpful.