In the cultural sphere the party and government have promoted pride in the ancient Bulgarian heritage but have regulated art, music, and literature in order to bring about conformity with the Soviet-developed doctrine of Socialist Realism. Throughout the communist era there have been periods of freeze and thaw in the controls imposed on artists and intellectuals, but the periods of greatest restriction in later years have not equaled the severity of the Stalinist times. In the 1960s and early 1970s control has been exercised primarily through publishers, art galleries, theaters, and other outlets. Artists and intellectuals know that their work must pass through state-owned outlets if it is to be seen or heard; therefore, they exercise self-censorship to ensure acceptability. Other means of control are the professional unions that all artists, writers, and actors must join if their work is to be exhibited or published. The unions are run by the BKP and, in effect, become instruments through which the party promotes its cultural policies. For some artists conformity with ideological goals leads to upward social mobility, and some enjoy privileges and life-styles that are usually reserved for the ruling elite. For control of the general population the government relies on the regular police, court, and penal systems, which are supplemented by state security police, paramilitary police auxiliaries, and militarized border guards. The regular police forces, the auxiliaries, and the state security police are all under the jurisdiction of the Ministry of Internal Affairs, whereas the border guards are subordinated to the army and are regulated by the Ministry of National Defense. Courts and penal institutions are under the Ministry of Justice. Also as means of control, the government sanctions and the party operates a number of mass organizations that affect or influence the lives of most people in the country. The Fatherland Front is a large umbrella organization that includes all other groups as well as individual members. The other mass organizations include trade unions, youth groups, athletic societies, and similar interest groups. Other than these officially sanctioned groups, there are no organizations permitted and, because the party retains control through the leadership positions, all organized activity in the country comes under BKP supervision. Such organizations also serve as upward channels of information through which the party hierarchy is able to keep in touch with popular opinion.