In all my SOPs I cited 2-6 papers by professors in the department. You can allude to specific work or specific projects without explicitly naming the grad student, e.g. "The recent work by Professor Johnson [1-3] on low-temperature titania nanoparticle sintering techniques appeals to me in particular because [blah blah blah]."
The NSF GRFP application wants GRE "subject codes." However, both the "Online Bulletin" and "Test Center and Code Lists" have been useless. Does anyone have a list of these codes? If so, please post them here!