Dissertations and theses can be found in a various databases. However the most comprehensive place to look is:
Once you know of a masters' thesis or PhD dissertation you want to read, how do you get a copy?
Typically, masters' theses and PhD dissertations can be found at the college/university library where the graduate student (author) received his/her degree.
UMass Boston theses are listed in UMBrella. Search the catalog by author, title of thesis, or by typing into the search box exactly this: University of Massachusetts at Boston Theses.
For non-UMass Boston theses & dissertations, just follow these steps: