Multiple copies are only purchased for high demand titles or titles authored by MSU faculty. Decisions to replace materials missing or damaged beyond repair are made on a case-by-case basis. Replacements are often purchased in electronic format but may be purchased in physical format if available and affordable for high-demand or important monographs and for journal issues if they are not available electronically. Multiple copies of outdated materials may be deselected, but unique materials are usually retained. Preservation decisions follow the general guidelines established by the Main Library.