Pakistani facilities are classified as central prisons, special prisons, district prisons, and subjails. Offenders are classified according to their personality, education, social status, and prior criminal record. Since the 1960's there has been a backlog of pre-trial detainees; this overcrowding has resulted in prison riots and problems in diet, hygiene, and security. Religious and general education are considered to be the best ways to motivate and rehabilitate offenders. Although there is a central training academy offering a number of courses, the facility lacks physical and other resources. Women inmates have unique problems, the most pressing of which is the lack of visits from family and friends. In 1978, new prison rules were adopted to improve jail administration; they are based on the United Nations Standard Minimum Rules for Treatment of Prisoners.