1) Your university's maths department must have a copy of that journal , or
2) In case it doesn't have it, it can get in contact with others universities to check which one has a copy.
3) Maths departments are usually subscribed to web services to access journals.
In the worst of all the cases, your thesis director may have to use some of its research budget to ask for a copy
from some other university. This is a standard fact and don't be shy of asking.