In 2002, my father received his US permanent residence card. Since then, he has traveled outside of the states for 238 days in 2003 and another 340 days in 2006, with INS permission. Each trip was longer than 180 days but less than the one year limit.
According to the n-400 form, he is required to submit proof of residence when applying for citizenship when there have been trips that lasted longer than 180 days since becoming a permanent resident. As a 70-year-old, he is not working and lives with me. What proof should he submit?