Case C-647/13: Judgment of the Court (Third Chamber) of 4 February 2015 (request for a preliminary ruling from the cour du travail de Bruxelles — Belgium) — Office national de l’emploi v Marie-Rose Melchior (Reference for a preliminary ruling — Social security — Conditions governing eligibility for unemployment benefit in a Member State — Taking into account periods of work completed as a member of the contract staff of an institution of the European Union which is established in that Member State — Treatment of days of unemployment for which an allowance is paid under the Conditions of Employment of Other Servants of the European Communities as working days — Principle of sincere cooperation)