A reference is a pointer to additional or more detailed information in related process areas and can accompany nearly any other model component. A reference is an informative model component.

For example, a reference that accompanies the specific practice “Select the subprocesses that compose the project's defined process based on historical stability and capability data” in the Quantitative Project Management process area is “Refer to the Organizational Process Definition process area for more information about the organization's process asset library, which might include a process element of known and needed capability.”