In 1996, CENELEC and the IEC signed the Dresden Agreement in order to create the necessary framework for an intensive consensus process between European and international standardization activities in the electricity sector. CEN works closely with the International Organization for Standardization (ISO) following the formal approval of the technical cooperation agreement between ISO and CEN (Vienna Agreement) of 1991. Therefore, the agreement defines two essential modes for the co-development of standards: the mode under the direction of ISO and that under the direction of CEN, in which documents prepared within one body are notified for simultaneous approval by the other body. ISO members can thus influence the content of the CEN standard and vice versa. The prioritisation of ISO work is also such that, in some cases, CEN needs to carry out urgent work in the European context, but less so at international level.