The date of filing of a European patent application shall be the date on which documents filed by the applicant contain:
(a) an indication that a European patent is sought;
(b) the designation of at least one Contracting State;
(c) information identifying the applicant;
(d) a description and one or more claims in one of the languages referred to in Article 14, paragraphs 1 and 2, even though the description and the claims do not comply with the other requirements of this Convention.