CELEX:62019CJ0866: Judgment of the Court (Third Chamber) of 21 October 2021.#SC v Zakład Ubezpieczeń Społecznych I Oddział w Warszawie.#Reference for a preliminary ruling – Social security for migrant workers – Regulation (EC) No 883/2004 – Article 52(1)(b) – Worker who has been employed in two Member States – Minimum period required by national law for acquisition of entitlement to a retirement pension – Account taken of the contribution period completed under the legislation of another Member State – Aggregation – Calculation of the amount of the retirement benefit to be paid.#Case C-866/19.