Request a Book lets you suggest resources for the Library to purchase. It can be useful if working on a very specific project.
Final year undergraduates, postgraduate students and staff can request material from other libraries as Interlibrary Loans. You can do this on Discover and instructions are here.
A class number (or class mark) is the numbers and letters on the spine of a book, showing where to find it in the Library.
Once you know the class number of a topic, you can use it to find other relevant resources.