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.
In above example, there were 4896 Visits out of 4901 Visits where Yahoo was the only referrer for the Visit.
Adding up the numbers 4896, 4311 and 4079 sums up to 13286 visits. This is the number shown in the total as well, confirming that the visits are mutually exclusive.