Distributive productive co-operative societies and their federations may, on their own demand, and with due regard to their constitution and character, be incorporated in the public economic system. ARTICLE 157. The labour forces of the nation are under the special protection of the Realm. The Realm shall draw up a uniform labour code. ARTICLE 158. Intellectual work, the rights of discoverers, inventors, and artists, shall be under the care and protection of the Realm. International agreements shall secure validity and protection in foreign countries for German intellectual, artistic, and technical creations. ARTICLE 159. Freedom of association with the object of guaranteeing and improving conditions of work and of employment shall be secured to all individuals and all professions. All compacts or measures which seek to limit or obstruct this freedom are illegal. ARTICLE 160. Any person occupying the position of employee or worker is entitled to have such free time as is necessary to avail himself of his rights as citizen, and, in so far as serious injury is not thereby done to his employment, such free time as is necessary to discharge honorary public offices conferred on him. His claims to compensation shall be determined by legislation. ARTICLE 161. The Realm, with the controlling co-operation of insured persons, shall create a comprehensive system of insurance for the maintenance of health and efficiency, for the protection of motherhood, and for provision against old age, infirmity, and change of circumstances. ARTICLE 162. The Realm shall support the principle of international regulation of the legal rights of workers, with the object of securing a uniform minimum of social rights to the working classes of mankind. ARTICLE 163. Every German is morally bound, without prejudice to his personal liberty, to make such use of his intellectual and physical capacities as shall be required by the common good. Every German shall be given the possibility of earning his living by economic labour. In so far as suitable employment cannot be found for him, provision shall be made for his necessary maintenance. Acts of the Realm shall make further provision. ARTICLE 164. Legislative and administrative measures shall be taken to encourage the independent middle class in agriculture, industry, and commerce and protect it against exploitation and extortion. ARTICLE 165. Workers and employees are called on to co-operate with the employers on a basis of equality, in regulating wage and work conditions and in furthering the general economic development of the forces of production. The organisations of either side and their agreements shall be recognised. Workers and employees shall, for the prosecution of their social and economic interests, receive legal representation in Works Councils, and also in District Workers' Councils organised by economic spheres, and in a Central Workers' Council.