1: Anthracite, bituminous, and brown coal. 2: Metal content. 3: Nitrogen content. 4: P_{2}O_{5} content 5: Active ingredients. 6: Fewer than 400 units. 7: Excluding house slippers and rubber footwear. SECTION IV. NATIONAL SECURITY CHAPTER 15 PUBLIC ORDER AND SECURITY To maintain order and to retain control of the population, party and governmental authorities rely on a number of police and security organizations that are able to exert physical force and, also, upon a group of large social organizations that are able to apply social pressures. When individuals, in spite of the efforts of the law enforcement agencies and the social organizations, engage in antisocial or criminal behavior, the courts are charged with handing down appropriate sentences, and the penal institutions are concerned with rehabilitating the individuals for eventual return to society as cooperative and productive members. People's Militia units throughout the country are the local police forces that enforce the laws, combat crime, and monitor the population. They are assisted in local law enforcement by part-time voluntary paramilitary auxiliaries and, in serious situations, by a small, centrally organized, full-time internal security force that can act as a light infantry unit and move quickly to any part of the country. State security police, evolved from the secret police of the 1940s and 1950s but much reduced in size, deal with crimes that are national in scope or that pose a threat to the society or its institutions. Authorities credit the security police with having almost eliminated the possibility of large-scale subversive activities. The militia, its volunteer auxiliaries, and the security units are organized within the Ministry of Internal Affairs. Border and construction troop organizations are administered separately. The Border Troops, charged with defense of the country's boundaries and with control of a border zone around the country's periphery, are a part of the Bulgarian People's Army and are under the Ministry of National Defense. The Construction Troops are labor forces, but the bulk of their personnel comes from the annual military draft, and they are organized into regular military units and are subject to military regulations and discipline.