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 each internship or job, include the name of the organization where you were employed, the city and state, the title of the positions held, the employment period for each job (include both months and years), and a short description of your accomplishments and technical skills used, listed in 3-4 max bullet points.