Article 798 Federal Labor Law

If the private document consists of a simple or photostatic copy, in the event of being objected to, the comparison or collation with the original may be requested; for that purpose, the offering party must justify the reasons or the impediment for not presenting it in the proceeding and specify the place where the original document is located. In this case the judge shall require the holder thereof to present it at the trial hearing; if that is not possible due to a legal provision or material impediment, he may commission the court officer or secretary to carry it out; in order to produce this means of perfection, the proceeding shall be carried out, as applicable, in accordance with the provisions of articles 827 and 829 of this Law.