Design And Methods: Case Study Research :

Researchers are encouraged to use triangulation by drawing from six sources of evidence: documentation, archival records, interviews, direct observations, participant-observation, and physical artifacts.

Typically "how" or "why" questions that explore contemporary phenomena within their real-life context. Case study research : design and methods

Defining what the "case" is (e.g., an individual, program, or organization) and establishing its boundaries. Researchers are encouraged to use triangulation by drawing