Memorandum: Determining Employer-Employee Relationship for Adjudication of H-1B Petitions, Including Third-Party Site Placements [open pdf - 1022KB]
"This memorandum is intended to provide guidance, in the context of H-1B-petitions, on the requirement that a petitioner establish that an employer-employee relationship exists and will continue to exist with the beneficiary throughout the duration of the requested H -1 B validity period."
HQ 70/6.2.8: AD 10-24
U.S. Citizenship and Immigration Services: http://www.uscis.gov/