In T 13/83 (OJ 1984, 428), a case decided prior to G 3/89 (OJ 1993, 117) and G 11/91 (OJ 1993, 125) (see in this chapter II.E.4. "Correction of errors in the description, claims and drawings – Rule 139 EPC" below), the board held that R. 88 EPC 1973 (R. 139 EPC) did not apply to a non-obvious correction of an error in the description or claims which resulted from an erroneous technical calculation. A correction of such an error was allowable under Art. 123(2) EPC 1973 if the amendment would be regarded by the skilled reader as clearly implied by the disclosure of the application as filed. If more than one arithmetical possibility of correction could be envisaged, the correction chosen had to be the one which the application as a whole clearly implied (see also T 784/96, which cites T 13/83).