The description should also mention any background art of which the applicant is aware, and which can be regarded as useful for understanding the invention and its relationship to the prior art; identification of documents reflecting such art, especially patent specifications, should preferably be included. This applies in particular to the background art corresponding to the first or "prior art" portion of the independent claim or claims (see III, 2.2).

The insertion into the statement of prior art of references to documents identified subsequently, for example by the search report, should be required, where necessary, to put the invention into proper perspective (T 11/82, OJ 12/1983, 479). For instance, while the originally-filed description of prior art may give the impression that the inventor has developed the invention from a certain point, the cited documents may show that certain stages in, or aspects of, this alleged development were already known. In such a case the examiner should require a reference to these documents and a brief summary of the relevant contents. The subsequent inclusion of such a summary in the description does not contravene Art. 123(2). The latter merely lays down that, if the application is amended, for example by limiting it in the light of additional information on the background art, its subject-matter must not extend beyond the content of the application as filed. But the subject-matter of the European patent application within the meaning of Art. 123(2) is to be understood - starting off from the prior art - as comprising those features which, in the framework of the disclosure required by Art. 83, relate to the invention (see also VI, 5.3).

References to the prior art introduced after filing must be purely factual. Any alleged advantages of the invention must be adjusted if necessary in the light of the prior art.

New statements of advantage are permissible provided that they do not introduce into the description matter which could not have been deduced from the application as originally filed (see VI, 5.3.4).

If the relevant prior art consists of another European patent application falling within the terms of Art. 54(3), this relevant prior document belongs to the state of the art for all Contracting States. This is the case even if the two applications do not share any commonly designated State, or the designation of commonly designated States has been dropped. (see IV, 8). The fact that this document falls under Art. 54(3) must be explicitly acknowledged. Thus the public is informed that the document is not relevant to the question of inventive step (see IV, 11.2). According to Rule 165, the above also applies to international applications designating EP, for which the filing fee pursuant to Rule 159(1)(c) has been validly paid and, where applicable, the translation into one of the official languages has been filed (Art. 153(3) and (4)) (see IV, 7.2).

For transitional provisions concerning the applicability of Art. 54(4) EPC 1973, see III, 8.1.