could someone please inform me of the letters requirements at most schools? is it 2 science and 2 non-science? i have 2 coming from research advisors, is that bad? what category do the research advisors go in(im guessing science)? is there a limit to the number of letters? i also may get a recc for a clinical MD for volunteer work...where does that go? some schools i may plan on applying to are: MCW, madison, NU, Uchicago, duke, HST, vanderbilt, JHU, etc...anyone have specific info on the letters required from these schools? any advice on anything mentioned would be great. thank god for SDN!