These can be online book sellers or shops in the street.
You may find the details of a useful book that isn't held by a local library. If you think it would be very useful, you could consider buying your own copy.
You could also consider browsing book shops or online book sellers to look for relevant publications.
Publishers often have their own websites which may include the contents pages of books or give overviews and reviews. These may help you identify relevant books - you can then check if they are in your library or buy a copy for yourself.