How to find reference information sources?

In comparison, a reference book or reference-only book in a library is one that may only be used in the library and not borrowed from the library. Many such books are reference works (in the first sense) which are usually used only briefly or photocopied from, and therefore do not need to be borrowed. Keeping them in the library assures that they will always be available for use on demand. Other reference-only books are ones that are too valuable to permit borrowers to take them out. Reference-only items may be shelved in a reference collection located separately from circulating items or individual reference-only items may be shelved among items available for borrowing.