USICS Information on Employment-Based Visas for Permanent Workers:

https://www.uscis.gov/working-in-the-united-states/permanent-workers

US Department of Labor Information on Permanent Labor Certification:

https://www.dol.gov/agencies/eta/foreign-labor/programs/permanent

USICS Policy Manual on Permanent Labor Certification:

https://www.uscis.gov/policy-manual/volume-6-part-e-chapter-6