5.1 Determination of the closest prior art 

Generally, the principles laid down in section GL/EPO G‑VII, 5.1, in the Guidelines for Examination in the EPO apply mutatis mutandis. The closest prior art is that which in one single reference discloses the combination of features which constitutes the most promising starting point for a development leading to the invention. In selecting the closest prior art, the first consideration is that it should be directed to a similar purpose or effect as the invention or at least belong to the same or a closely related technical field as the claimed invention. In practice, the closest prior art is generally that which corresponds to a similar use and requires the minimum of structural and functional modifications to arrive at the claimed invention.