Evaluating gray literature can be difficult because many of the standard indicators of quality, such as the reputation of the author, can be missing.
The AACODS Checklist is a well know and widely accepted instrument that you can use to assess what you find. It is made up of the following 6 elements:
- Authority: Is the author credible?
- Accuracy: Is it supported by documented and authoritative references? Is there a clearly stated methodology? Is it 'in line' with other work on the same topic
- Coverage: Have limitations been imposed and are these stated clearly?
- Objectivity: Can bias be detected?
- Date: Can't find the date? Rule of the thumb is to avoid such material
- Significance: Is it relevant? Would it enrich or have an impact on your research?