This is a very common RFE. So please do not panic. 198151's suggestions are pretty good. Actually I feel that your citations (about 35) are pretty good. I have seen quite a few cases approved with only 5-10 citations.
However, one thing you need to know is that ONLY recommendation letters are not enough. You need to collect some objective evidence. You need to emphasize the influence and impact of your citation. The number of citation is only one aspect. The quality of citation is also important. For example, a big guy cited your paper and gave you very good feedback. This kind of evidence is good. Also, review paper is helpful.
My email is fsa2000@gmail.com if you have more questions.