Semiconductor Doping Question
There's often lots of typos in books. I noticed plenty in my semiconductor book as well. It's frustrating as heck. You might want to confirm these typos with the professor. If enough people (hopefully professors) let the author know about the error, they'll get fixed in the next versions of the book.

But yes, \$ N_D \$ = donor concentration, \$ N_A \$ = acceptor concentration.