The date of filing of a European patent application shall be the date on which the documents filed by the applicant contain:
an indication that a European patent is sought;
information identifying the applicant or allowing the applicant to be contacted; and
a description or reference to a previously filed application.
A reference to a previously filed application under paragraph 1(c) shall state the filing date and number of that application and the Office with which it was filed. Such reference shall indicate that it replaces the description and any drawings.
Where the application contains a reference under paragraph 2, a certified copy of the previously filed application shall be filed within two months of filing the application. Where the previously filed application is not in an official language of the European Patent Office, a translation thereof in one of these languages shall be filed within the same period. Rule 53, paragraph 2, shall apply mutatis mutandis.