1. In any proceedings before the Office the means of giving or obtaining evidence shall include the following:
(a) hearing the parties;
(b) requests for information;
(c) the production of documents and items of evidence;
(d) hearing witnesses;
(e) opinions by experts;
(f) statements in writing, sworn or affirmed or having a similar effect under the law of the State in which the statement is drawn up.
2. The relevant department of the Office may commission one of its members to examine the evidence adduced.
3. If the Office considers it necessary for a party, witness or expert to give evidence orally, it shall issue a summons to the person concerned to appear before it.
4. The parties shall be informed of the hearing of a witness or expert before the Office. They shall have the right to be present and to put questions to the witness or expert.