Policy Memorandum: Fee Waiver Guidelines as Established by the Final Rule of the USCIS Fee Schedule; Revisions to Adjudicator's Field Manual (AFM) Chapter 10.9 (AFM Update AD11-05) [open pdf - 111KB]
"This Policy Memorandum (PM) provides guidance on processing fee waiver requests filed pursuant to 8 CFR 103.7(c) as amended by changes made in the final rule 'U.S. Citizenship and Immigration Services Fee Schedule,' published in the Federal Register (FR) on September 24, 2010. See 75 FR 58961."
Policy Memorandum: PM-602-0011
U.S. Citizenship and Immigration Services: http://www.uscis.gov/