USTB is made possible through the contribution of several labs around the world. It contains pieces of intellectual property from many authors, and because of that different references must be cited depending on your use of USTB. There are three kinds of intelectual property that must be acknowledged: datasets, processes, and the toolbox itself.
USTB hosts several datasets that can be downloaded from this section. Datasets have associated a reference that must be cited if you want to use it in your article or thesis. The reference is displayed in the property reference of the corresponding UFF class (normally uff.channel_data or uff.beamformed_data) but also in the dataset download page.
The backbone of USTB are its processes. A process is an abstract class that implements some kind of processing or algorithm. For instance a process can be a delay-and-sum beamformer, a coherent factor computation, a clutter filter, an edge detector, etc. All these processes have associated a reference property that must be cited if you want to use that process in your work. Note that sometimes more than one process is used in the processing chain; every process process must be cited.
The USTB toolbox should be cited as well. Please use the reference from the proceedings of the IUS (IEEE International Ultrasonics Symposium) 2017:
Authors vs implementers
Processes also have a implemented_by property. In many cases algorithms are not implemented by their original authors. There is no mechanism yet to cite implementations, unless the implemention itself is a piece of intellectual property and has an associated reference. But implementers can be acknowledged in the acknowledgements section of your article or thesis.