In T 166/04 the board held that the late introduction of additional prior art documents together with an invitation to oral proceedings was not necessarily improper, even if they formed part of a critical argumentation. The board considered that the time frame of two and a half months for the applicant to respond was in conformity with R. 71(1) EPC 1973 (R. 115(1) EPC) and was not unduly short. Further, apart from the non-extendable time limit, the appellant had had an opportunity to respond to the summons in writing as if he had responded to a communication under Art. 96(2) EPC 1973 (Art. 94(3) EPC), which he had actually done by submitting amendments and further arguments. In addition, the board pointed out that the applicant had decided not to participate in the first-instance oral proceedings during the course of which he could have made further submissions.