Rule 121
Commissioning of experts

(1) The European Patent Office shall decide in what form the opinion of an expert whom it appoints shall be submitted. 

(2) The terms of reference of the expert shall include: 

(a) a precise description of his task; 

(b) the period specified for the submission of his opinion; 

(c) the names of the parties to the proceedings; 

(d) particulars of the rights which he may invoke under Rule 122, paragraphs 2 to Rule 122, paragraphs 4.

(3) A copy of any written opinion shall be submitted to the parties. 

(4) The parties may object to an expert. The department of the European Patent Office concerned shall decide on the objection.