Judgment of the Court of 31 May 2001 in Case C-43/99 [reference for a preliminary ruling from the Conseil supérieur des assurances sociales (Luxembourg)]: Ghislain Leclere and Alina Deaconescu v Caisse nationale des prestations familiales (Regulations (EEC) Nos 1408/71 and 1612/68 — Luxembourg maternity, childbirth and child-raising allowances — Residence condition — Rights of a person receiving a pension but not resident in the Member State responsible for the pension — Family allowances and family benefits — Concept of "worker" and "social advantage")