Reviewing and eliminating any ambiguities in the claims and description which are not necessary to refute substantiated grounds of opposition is not part of the review of the contested decision carried out during opposition appeal proceedings. In the event of ambiguities in the claims which are not connected to changes in the granted documents, Art. 69 EPC 1973 stipulates that the description and drawings must be used to interpret the claims, not that the claims must be changed (T 481/95).