When a research statement of a fixed page length is required, are references counted in the page length?
Unlike the NSF, where references often do not count towards page limits, I would assume that references do count as part of the 3-page limit for a research statement in a job application. 

At the same time, few research statements I have seen in mathematics are as thoroughly referenced as an NSF proposal. The main goal of a research statement when applying for a job is to describe your own research and to demonstrate that you will be able to meet the research expectations of the job. As such, you want to keep the research statement relatively brief.

If you really need more than 3 pages including references, you should email the chair of the search committee to find out if it is acceptable.