Judgment of the Court (Sixth Chamber) of 20 June 2002 in Case C-401/99 (Reference for a preliminary ruling from the Schleswig-Holsteinisches Oberverwaltungsgericht): Peter Heinrich Thomsen v Amt für ländliche Räume Husum (Council Regulation (EEC) No 3950/92 — Additional levy in the milk and milk products sector — Reference quantities — Conditions of transfer to lessor in the event of the surrender of leased lands — Notion of "producer")