KEYWORD SEARCHES: Try keywords searches to find a few likely books, then view and click on the "official" subject headings in the full record. For example: If you do a keyword search on UNITED STATES MEXICO BORDER, and look at the full record of relevant items, you'll see the Subject term MEXICAN-AMERICAN BORDER REGION. Clicking on that Subject heading, or typing that exact phrase as a Subject or General Subject search, will bring up many hundreds of results.
SUBJECT HEADINGS: Library of Congress Subject Headings (LCSH) are the subject terms used to catalog books in most academic libraries. They are often not intuitive, and must be entered very precisely; starting out a search by doing a General Subject search on Roger, and guessing at a Subject heading, often produces no results.
Roger: UCSD's library catalog listing books, government publications, maps, audiovisuals, periodicals, etc., owned by UCSD. No articles listed, but has links to electronic journals, or anything else online. If UCSD copy is unavailable, or we do not own, "Search in Circuit" looks in local university and San Diego County Public Library catalogs. There is usually a 24-48 hour delivery to UCSD. If no Circuit library has an available copy, "Search in Melvyl" may locate another UC campus that has a copy that can be sent to UCSD. You can also use 
for recalling or putting holds on UCSD books, but that method may take longer than Circuit or even Melvyl.
Circuit: This is the combined catalogs of UCSD, SDSU, USD, and the San Diego County Public Library system, for books only. Books may be Requested online and are usually delivered the next day, except for weekends. The public library books can take longer. Books are checked out, renewed, and otherwise treated as UCSD materials.
Melvyl: Combined search of all UC Libraries, books, government documents, periodicals subscriptions (but not content of periodicals), and more. "Request" button activates Interlibrary loan service; delivery from 2-3 days (Southern California campuses) to 5-7 days (Northern campuses). NOTE: Melvyl is now part of the WorldCat, a combined "world catalog" of more than 12,000 libraries around the United States and worldwide. The same button will get them for you; it just takes a little longer.
HathiTrust: The HathiTrust Digital Library is a digital preservation repository and an access platform. It provides long-term preservation and access services for public domain and copyrighted content from a variety of sources, including Google, the Internet Archive, Microsoft, and in-house partner institution initiatives. Content is full-text searchable; most items published before 1923 are full-text viewable and downloadable.
