Virtual Library of Science (VLS) is a program of purchasing and making available world knowledge resources in the form of electronic journals, books and databases to Polish academic and scientific institutions. The program is co-financed by the Ministry of Science and Higher Education and implemented mostly by the ICM. Within the VLS, access to resources on publisher's servers is purchased within the framework of annually renewed licenses, but a large part of the resources is archived on an ongoing basis on Infona's server in ICM, which ensures the possibility of indefinite use of archives in case of temporary or permanent loss of access to publisher's servers, in particular if the license is not continued.