The same level of skill has to be applied when, for the same invention, the two questions of sufficient disclosure and inventive step are being considered (T 60/89, OJ 1992, 268; T 694/92, T 187/93, T 412/93). However, the standard of disclosure required for amendments by Art. 123(2) EPC 1973, namely that of being directly and unambiguously derivable, is inappropriate, the criterion being that it must be possible to reproduce the invention on the basis of the original application documents without any inventive effort and undue burden (T 629/05; cited in T 79/08).
The skilled person may use his common general knowledge to supplement the information contained in the application (T 206/83, OJ 1987, 5; T 32/85, T 51/87, OJ 1991, 177; T 212/88, OJ 1992, 28; T 772/89) He may even recognise and rectify errors in the description on the basis of such knowledge (T 206/83, OJ 1987, 5; T 171/84, OJ 1986, 95; T 226/85, OJ 1988, 336). Textbooks and general technical literature form part of the common general knowledge (T 171/84, T 51/87, T 580/88, T 772/89). However, information which can only be obtained after a comprehensive search is not to be regarded as part of the common general knowledge (T 206/83, T 654/90). According to the board in T 475/88, in the event of a dispute a claim of common general knowledge must be backed up by evidence. As a rule, demonstrating that the knowledge in question can be obtained from a textbook or monograph will be sufficient.
Patent specifications cannot normally contribute to the sufficiency of the disclosure unless they are available to the skilled reader of the patent in question (T 171/84, OJ 1986, 95). By way of exception, however, patent specifications and scientific publications may be considered to form part of the common general knowledge where the invention is in a field of research so new that the relevant technical knowledge is not yet available from textbooks (T 51/87, OJ 1991, 177; see also T 772/89, T 676/94). In T 676/94 the board considered that the question whether or not the contents of a technical periodical formed part of the average knowledge of a skilled person when assessing sufficiency of disclosure, should be answered on the basis of the facts and evidence in each particular case.