Under R. 139 EPC (formerly R. 88 EPC 1973), mistakes in any document filed with the EPO may be corrected on request. However, if the request for such correction concerns the description, claims or drawings, the correction must be obvious in the sense that it is immediately evident that nothing else would have been intended than what is offered as the correction. Re corrections under R. 139, second sentence, EPC see also chapter II.E.4. "Correction of errors in the description, claims and drawings – Rule 139 EPC".