To get visits with a single referring domain, it is required to create a segment that removes visits with referring domain not equal to each particular domain of interest.
This means, each domain that that is of interest, needs a condition in the segment. For example to find the visits where users came in through only Yahoo.com the segment definition would be:
To expand this segment to other domains, insert an exclude container for each domain that is required:
To validate the information, run the referring domain report with the Visits metric
Normally the visits for the individual referring domains sum up to a larger number than the total visits. This is because a single visit can have more than one referring domain.
When this segment is applied, each referring domain is showing mutually exclusive visits, and so the values should add up.