dismissals effected by an employer for one or more reasons not related to the individual workers concerned where, according to the choice of the Member States, the number of redundancies is: - either, over a period of 30 days: (1) at least 10 in establishments normally employing more than 20 and less than 100 workers; (2) at least 10 % of the number of workers in establishments normally employing at least 100 but less than 300 workers; (3) at least 30 in establishments normally employing 300 workers or more; - or, over a period of 90 days, at least 20, whatever the number of workers normally employed in the establishments in question, licenciement d'un certain nombre, sinon de tous les employés d'une entreprise