Special rule relating to multiple support agreements

For purposes of paragraph (1)(C), over one-half of the support of an individual for a calendar year shall be treated as received from the taxpayer if—

(A) no one person contributed over one-half of such support,

(B) over one-half of such support was received from 2 or more persons each of whom, but for the fact that any such person alone did not contribute over one-half of such support, would have been entitled to claim such individual as a dependent for a taxable year beginning in such calendar year,

(C) the taxpayer contributed over 10 percent of such support, and

(D) each person described in subparagraph (B) (other than the taxpayer) who contributed over 10 percent of such support files a written declaration (in such manner and form as the Secretary may by regulations prescribe) that such person will not claim such individual as a dependent for any taxable year beginning in such calendar year.