Common general knowledge can come from various sources and does not necessarily depend on the publication of a specific document on a specific date. An assertion that something is common general knowledge need only be backed by documentary evidence (for example, a textbook) if this is contested (see G-IV, 2).
A single publication (e.g. a patent document, but also the content of a technical journal) cannot normally be considered as common general knowledge (see T 475/88). In special cases, articles in technical journals can be representative of common general knowledge (see T 595/90). This applies in particular to articles providing a broad review or survey of a topic (see T 309/88). For the skilled person addressing the problem of bringing together certain starting materials, the conclusions of research on these materials carried out by only a very few manufacturers form part of the relevant general technical knowledge, even if the studies in question have only been published in technical journals (see T 676/94). Another exception is that it can also be the information contained in patent specifications or scientific publications, if the invention lies in a field of research which is so new that the relevant technical knowledge is not yet available from textbooks (see T 51/87).
Basic textbooks and monographs can be considered as representing common general knowledge (see T 171/84); if they contain references which direct the reader to further articles dealing with specific problems, these articles too may be counted as part of such knowledge (see T 206/83). Here it should be remembered that information does not become common general knowledge because it has been published in a particular textbook, reference work, etc.; on the contrary, it appears in books of this kind because it is already common general knowledge (see T 766/91). This means that the information in such a publication must have already become part of common general knowledge some time before the date of publication.