Conducted by the Defense for Children International the Netherlands, the study involved a literature search and in-depth questionnaires completed by key persons and organizations in 25 nations. The study defined "deprivation of liberty" as "any form of detention or imprisonment or the placement of a person in a public or private custodial setting, from which this person is not permitted to leave at will, by order of any judicial, administrative, or other public authority." One of the most serious concerns was the estimate that more than 1 million children are deprived of their liberty worldwide, which clearly violates United Nations Rules for the Protection of Juveniles Deprived of Their Liberty as well as the Convention on the Rights of the Child. Both of these international documents provide that arrest, detention, or imprisonment should be used only as a last resort and for the minimum necessary period and be limited to exceptional cases. The second major concern stemmed from evidence that children are held under arrest and in detention or imprisonment under deplorable conditions worldwide. Such conditions include crowding and inadequate water, toilets, food, health care, recreation, and educational opportunities. There were also numerous reported cases of torture, mistreatment, sexual abuse, psychological abuse, and neglect. Report recommendations are to put no children under age 15 in prison, to use alternatives for imprisonment, to focus on prevention, and to improve the conditions of children in closed institutions.