Witnesses and experts who are summoned by and appear before the EPO are entitled to appropriate reimbursement, by the EPO, of expenses for travel and subsistence (see IV, 1.10.3). This applies even if the witnesses or experts are not heard, e.g. where evidence is to be produced concerning an alleged prior use and shortly before the taking of evidence such prior use is substantiated by a document already published. Witnesses and experts may be granted an advance on their expenses for travel and subsistence. Witnesses and experts who appear before the EPO without being summoned by it but are heard as witnesses or experts will also be entitled to appropriate reimbursement of expenses for travel and subsistence.