Amendments to a patent (application) are bound to strict rules under the European Patent Convention (EPC). According to Art. 123(2) of the EPC, a European patent (application) may not be amended in such a way that it contains subject-matter which extends beyond the content of the application as filed. Adding subject-matter which is not disclosed would give an applicant an unwarranted advantage and could be damaging to the legal security of third parties. (G 1/93, OJ 1994, 541) The ‘gold standard’ of the European Patent Office’s Board of Appeal  is that any amendment can only be made within the limits of what a skilled person would derive directly and unambiguously, using common general knowledge, and seen objectively and relative to the date of filing, from the whole of the documents as filed (G 3/89, OJ 1993,117; G 11/91, OJ 1993, 125).