Text in periodical
Gladney, Henry M. – «Digital preservation in a national context : questions and views of an outsider». – D-Lib Magazine [on line]. – Vol. 13, no. 1/2 (Jan./Feb. 2007). – N. p. {{www.dlib.org}}
Digital document
Hedstrom, Margaret et al. – Invest to save : report and recommendations of the NSF-DELOS working group on digital archiving and preservation [digital document]. – Sophia Antipolis : DELOS Network of Excellence on Digital Libraries ; Arlington : National Science Foundation, 2003. – 38 p. – Acrobat (PDF) file. {{delos-noe.iei.pi.cnr.it}}