On the basis of the partially preserved records it is likely that most of the children and children with mothers that came to Sweden with UNRRA White Boats left Sweden starting in May 1946. Swedish authorities did tremendous and efficient work to find eventual relatives for the children who came to Sweden without any assistance.
The information about a group of children that came from the Piotrków Trybunalski ghetto could be obtained from the persons who knew the children and the families already when in Piotrków ghetto or from the camps where the children were imprisoned before, in many cases with their parents that died before or shortly after the liberation. In many cases, the children themselves, full orphans, had no idea about the names of their parents, the day and place of birth, etc.