search了一下Pub 519, 可能就是这个：
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Statement required to make the first-year choice. You must attach a
statement to Form 1040 to make the first-year choice. The statement must
contain your name and address and specify the following.
- That you are making the first-year choice.
- That you were not a resident in 2006.
- That you are a resident under the substantial presence test in 2008.
- The number of days of presence in the United States during 20
