-- The deduction under subsection (a) shall only be allowed for purposes of this chapter. (congress.gov)
The main purpose of a chapter heading is to introduce and set the tone for the upcoming chapter of the book. (adazing.com)
If the taxpayer is a nonresident alien individual for any portion of the taxable year, this section shall apply only if such individual is treated as a resident alien of the United States for purposes of this chapter by reason of an election under subsection (g) or (h) of section 6013. (law.cornell.edu)