Dear ***,
Thank you for your letter. In principle, I would be interested to have you join my group for a year, but I'm afraid it won't be possible under this program. We have looked into this before, because other students have proposed to come here with sponsorship by the CSC. Unfortunately, the level of support provided by the fellowship is only about half of the actual cost of living here. Moreover, there are fees required by Princeton University for visiting students. Therefore, it is not possible to invite you.
I'm sorry that I can't be more encouraging.
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