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.
In addition, functional or combination resumes may also be useful if you are trying to draw the readers attention away from something – namely, large gaps in your work history or detours into unrelated fields.