You can search the Library catalogue to find journals: https://swims.inforlib.uk/iguana/www.main.cls?surl=HEE
The catalogue will list both journals that are available in print and electronically in all libraries in the SWIMS (South West) network, but you can restrict your search to just the Royal Berkshire Trust.
You can also see the e-journals that are available by logging into your OpenAthens account.
