If you can't get access to the book or article you need, you could try requesting it through the Inter Library Loans service (ILL).
This is a free service available for all staff and students (but check allowances for your own situation):
Foundation, first and second year students - 5 ILL requests per year
Final year students - 15 ILL requests per year
Postgraduates and staff - 30 ILL requests per year.
Access the request form via the Library Portal (sign into the Portal first): Inter Library Loans. Just in fill in the details of the item you require.