References. It is assumed that you have references if you have previous employment history. It is not at all necessary to include “references available upon request”, adding this is actually a potential deterrent. Potential employers will ask you for your references later on in the interview process if they see fit. Of course, if references are asked for within the application process, provide them - just not on your resume.
For example, if you took a job and only stayed there for a month or so, you wouldn’t want to include that position. If you’ve been out of college for more than five years, it’s generally best to remove any internships you’ve had, assuming you have other professional work experience to fill the gap.