DanMcS said:In order: No; the SRDs; you can't refer to the books by name but can refer to anything in the SRD; and yes, the d20 modern SRD is OGLed.
One mistake: if you're not using the D20STL, there is no explicit rule on using the titles of the WotC D&D books. However, there is a clause forbidding using trademarks to indicate "compatibility or co-adaptability" [without permission]. Nonetheless, the only WotC book with a trademark in the title is Dungeon Master's Guide. Therefore, if you're not using teh D20STL, you can freely refer to most of the WotC books (D&D and otherwise).