@TechReport{di-fcul-tr-05-21,
    author = {Daniel Gomes and Mário J. Silva},
    title = {On URL and content persistence},
    institution = {Department of Informatics, University of Lisbon},
    month = {December},
    year = {2005},
    type = {DI/FCUL TR},
    number = {05--21},
    url = {http://www.di.fc.ul.pt/tech-reports/05-21.pdf}
}