Further official sources of FRMS information (which is scattered) for your research study:
FAA Fatigue Risk Management
https://www.faa.gov/about/initiatives/maintenance_hf/fatigue
View publications and articles about human fatigue, shift work, maintenance personnel fatigue, and fatigue risk management.
https://www.faa.gov/about/initiatives/maintenance_hf/fatigue/publications
FRMS Fatigue Risk Management in Aviation Maintenance: Current Best Practices and Potential Future Countermeasures
https://www.faa.gov/sites/faa.gov/files/data_research/research/med_humanfacs/oamtechreports/201110.pdf
Maintainer Fatigue Risk Management
https://www.faa.gov/documentlibrary/media/advisory_circular/ac_120-115.pdf
FRMS for business aviation:
https://nbaa.org/wp-content/uploads/2018/01/the-alert-crew-fatigue-awareness-in-flight-operations.pdf