The HOLLIS Catalogs are the main public gateways to the vast resources available through Harvard Library, including materials physically held by the 78 individual libraries that comprise the library system - among them the Biblioteca Berenson - as well as millions of licensed materials accessible online. Harvard's aggregate library holdings include over 13 million monographs, 625,000 journals,19 million volumes, 1 million e-books, 10 million photographs, 160,000 musical scores, 150,000 sound recordings, and 200,000 linear feet of unique archives and manuscript collections. HOLLIS Classic, the older public catalog, gives access to most, but not all, of the library's resources, and offers both simple and highly specific searching possibilities. HOLLIS+ is Harvard Library's new discovery platform, which was introduced in August 2014. It provides aggregated access both to Harvard materials and licensed items. In other words, using HOLLIS+ you can search books, articles, and non-textual materials together.
Note that finding aid data from the OASIS catalog (archives and manuscripts) and visual image data from the Hollis Images are indexed in HOLLIS+.