An independent expert of mine probably sent his reference letter directly to the immigration service center. I have contacted him several times, but he just doesn't reply me. Obviously it is difficult to ask him to sign and send a copy to me. Since he is a big man in my field, his letter is significant to my NIW-RFE petition. I am wondering how the service center deals with this kind of letters, throw them away? return them? or put them into petitioners' package? Thanks a lot!