3. However , the products in Group III may be imported Article 1 into the Community in accordance with the arrangements established by this Agreement on production of a declaration 1. The competent authorities of the Community by the exporter on the invoice or other commercial document undertake to inform Czechoslovakia of any changes in the relating to the products to the effect that the products in tariff and statistical nomenclatures before the date of their question originate in Czechoslovakia within the meaning of entry into effect in the Community . the relevant rules in force in the Community . 2. The competent authorities of the Community undertake to inform Czechoslovakia of any decisions relating Article 3 to the classification of products subject to the Agreement within one month of their adoption at the latest. Such The certificate of origin shall be issued only on application communication shall include : having been made in writing by the exporter or , under the exporter's responsibility , by his authorized representative . ( a ) a description of the products concerned ; The competent governmental authorities of Czechoslovakia ( b ) the relevant category and the related tariff and statistical shall ensure that the certificate of origin is properly references ; completed and for this purpose they shall call for any necessary documentary evidence , or carry out any check ( c) the reasons which have led to the decision . which they consider appropriate. 3. Where a decision on classification results in a change of classification practice or a change of category of any product Article 4 subject to the Agreement , the competent authorities of the Community shall provide 30 days' notice , from the date of Where different criteria for determining origin are laid downthe Community's communication , before the decision is put for products falling within the same category , certificates or