@misc
{TN_libero_mab2,
author = {
Hofferth, Sandra L.
},
title = {
Changes in American children´s time - 1997 to 2003
},
publisher = {Forschungsinstitut Freie Berufe},
isbn = {1860-9937},
year = {2009},
url = {
http://slubdd.de/katalog?TN_libero_mab2
}
}