The "state of the art" for the purposes of considering inventive step is as defined in Art. 54(2) (see G‑IV, 1). It is to be understood as concerning such kind of information as is relevant to some field of technology. It does not include later published European applications referred to in Art. 54(3). As mentioned in G‑IV, 3, "date of filing" in Art. 54(2) means date of priority where appropriate (see F‑VI). The state of the art may reside in the relevant common general knowledge, which need not necessarily be in writing and needs substantiation only if challenged (see T 939/92).