Case T-753/20: Judgment of the General Court of 14 December 2022 — Green Power Technologies v Commission (Arbitration clause — Seventh Framework Programme for research, technological development and demonstration activities (2007-2013) — Grant agreement — Eligible costs — OLAF report finding certain expenses incurred to be ineligible — Repayment of sums paid — Burden of proof — Regulation (EU, Euratom) No 883/2013 — Obligation to state reasons — Unjust enrichment — Action for annulment — OLAF report — Act not open to challenge — Inadmissibility)