This paper explains that about digital documentations treatment we must read the Ann Okerson’s literature: in fact, she has a lot of relevant experience in this topic and gives us many suggestions for working with. Recently, Ann Okerson took part in a meeting in Geneva (Switzerland). This paper analyses what she said in that occasion and  from working groups at the University of Padua, too. 
Ann Okerson, since 1995 joined at Academic Library of Yale, with her studying and articles, defined a turning point about subscriptions to digital journals thanks to the cooperative contracts.
During her fifteen-year experience, she has been studing the development of collections as digital journals, in particular about negotiation. She has been playing a fundamental goal for NERL (NortEast Research Libraries) in the United States of America, which involves 18 academic libraries and centres of research.