officer of the body corporate, or by any other person who satisfies the registrar that he or she is authorised to sign the document, and the document shall bear the seal of the body corporate. (3) A document purporting to be signed for or on behalf of an association of persons may be signed by any person who satisfies the registrar that he or she is authorised to do so. (4) The registrar may, whenever he or she deems it necessary, request evidence of authorisation to sign. 8. Measures, terminology and signs. (1) Units of weight and measures shall be expressed in terms of the metric system. (2) Temperatures shall be expressed in degrees centigrade (Celsius). (3) Density shall be expressed in metric units. (4) For indications of heat, energy, light, sound and magnetism, as well as for mathematical formulae and electrical units, rules in general use shall be observed; and for chemical formulae the symbols, atomic weights, and molecular formulae, in general use, shall be employed. (5) In general, only technical terms, signs and symbols generally accepted in the art should be used. (6) The terminology and the signs used shall be consistent throughout the application. 9. Number of copies and physical requirements. (1) The application and any accompanying statements or documents shall be filed in triplicate, but the registrar may require the applicant to supply additional copies. (2) All elements of the application shall be so presented as to admit of direct reproduction by photography, electrostatic processes, photo offset and microfilming.