Funny you mention that, I am planning on doing my PhD on a terrorism related topic. I figure the underlining will come in handy when I get to that point.
You're very welcome. I think I will try to do the same sort of thing with a few other books I have read recently.
I tried several different marking methods--colors, symbols, margin lines etc.
In the end, the most functional thing was:
WHATEVER HAD THE MOST INK next to it!
I DID FIND IT VERY USEFUL TO RUN THE LINE FROM THE MARKED PART DOWN THE EDGES OF THE BOOK SO THAT I COULD GO FROM A CLOSED BOOK TO THE PARAGRAPHS OR SENTENCES WITH THE MOST INK VERY QUICKLY AS THOUGH THE BOOK WAS THUMB INDEXED. *THAT* saved tons of time. The most important parts I used 3-5 lines on the edges of the book. And, I used different colors every so many pages just to make such easier to decipher.
The same could be useful to help us on this thread with reference books we might have at hand.