Case C-2/17: Judgment of the Court (Tenth Chamber) of 28 June 2018 (request for a preliminary ruling from the Tribunal Superior de Justicia de Galicia — Spain) — Instituto Nacional de la Seguridad Social v Jesús Crespo Rey (Reference for a preliminary ruling — Agreement between the European Community and its Member States, of the one part, and the Swiss Confederation, of the other, on the free movement of persons — Social security for migrant workers — Regulation (EC) No 883/2004 — Paragraph 2 of the section ‘Spain’ in Annex XI — Retirement pension — Method of calculation — Theoretical amount — Relevant contribution basis — Special agreement — Choice of contribution basis — National legislation requiring the worker to make contributions in accordance with the minimum contribution basis)