USCIS’ Handbook for Employers – Instructions for Completing Form I-9 (Employment Eligibility Verification Form)
VIA USCIS
A 1/05/11 edition of the M-274, Handbook for Employers, Instructions for Completing Form I-9 (Employment Eligibility Verification Form) from USCIS.
Available here (PDF)
The U.S. Immigration Law Blog by Ashwin Sharma 