Search engine for academic literature, note that it only search a small fraction of what is available through specialized databases. Particularly useful to find articles and books that cite a particular article/book
Search engine for books and journals digitized by Google and digital editions from many publishers, note that it is limited to digital/digitized materials. Use advanced search to search by title.
Use the advanced search in Settings to limit by file type, image color, license, image type, or geographical location