It is established case law that features not mentioned in the application documents themselves but in a document to which they refer may be incorporated into a patent claim if they unequivocally form part of the invention for which protection is sought. However, all the essential structural features thus disclosed which belong together must be incorporated into the claim; it is not permissible to single out a particular one (T 6/84, OJ 1985, 238; cited in numerous decisions).
In T 288/84 (OJ 1986, 128), the board held that where an invention relates to the improvement of prior art originally cited in the description of the invention, a feature described in broad terms in the cited document but not mentioned expressly in the invention is sufficiently disclosed if it is realised in the examples of the invention in the form of an embodiment also mentioned in the reference document.
An invention is also sufficiently disclosed if reference is made to another document in the patent specification and the original description, and the skilled person can obtain from this cross-reference the information required to reproduce the invention but not disclosed in so many words in the description itself (T 267/91, T 611/89). In T 920/92 the board held that this applied irrespective of the language in which it was drafted; (here Japanese).
However, where the reference document was possibly short-lived advertising material, the applicant was wise to incorporate the published information explicitly rather than by mere reference (T 211/83, cited in T 276/99).
In T 737/90 it was explicitly stated that a reference to another document can only be taken into account if the document referred to can be unambiguously identified and the relevant addressees have ready access to it. This depends solely on the facts of the case. Following T 737/90, the board in T 429/96 confirmed that a document incorporated by reference into the text of a European patent application had to become available to the public at the latest on the publication date and not on the filing date of the European patent application, in order to be taken into account for the purposes of Art. 83 EPC 1973.
In T 341/04, the question was whether a referenced document, which could be unambiguously identified at the date of filing of the document containing the reference by its document number, but which document itself was "missing" in the sense that it was not available at said date of filing, could be "taken into account" for the purpose of Art. 83 EPC 1973 by relying on information present in a family member of the referenced document. The board answered in the affirmative.