What reference books sit on your desk?

Guest blogger Jason Sanford often rants on his website at www.jasonsanford.com. His fiction has been published in Interzone, Year's Best SF 14, Analog, Intergalactic Medicine Show, Pindeldyboz, and other places, and has won the 2008 Interzone Readers' Poll and a Minnesota State Arts Board Fellowship.

So you dare call yourself a writer! If that's the case, here's my question: What reference books sit on your desk?

And yes, we know all about that amazing resource called the internet. And yes...