To sharpen tactical vision

I have good tactical vision on board, can find combinations. but i want to pracitse more on that, there is many websites for solving tactical problems, but i dont want to looking on computer screen continuesly for hours, so i want to buy book. so Please anyone suggest me a name of book that may contain very hard, very tough and very difficult tactical problems. Thanks you very much. 

http://chessteaching.x10.mx/1001-brilliant-checkmates/

http://chessteaching.x10.mx/winning-chess-sacrifices-and-combinations/

1001 check mates and winnig combinations are available,may be with different ideas. Still it is available as you search the net.

As with the computers,there are screens available as well as LED monitors and and I bet you that you better be used to computers. The past era is over and unless you  are used to it unlikely you will get the edge over other in this modern era. ( even many college exams will takes hours together across the world are now  on computers. ( some takes even 12 Hours )

Try Ray Cheng's Practical Chess Exercises.  Unlike most tactics books that are divided into sections so you know what motifs you're working on, Cheng's book simply presents a position you have to solve.  Tough puzzles, recommended (and introduction by) by John Watson.  Coach Heisman gives it a big thumbs up as well.

Thanks Jdannyboy and Baddogno, your message is really helpful to me. i m looking on websited you suggest and Ray cheng's book review. thanks :)

Try http://www.amazon.com/Improve-Your-Chess-Tactics-Practical/dp/9056913344/ref=sr_1_1?s=books&ie=UTF8&qid=1356182664&sr=1-1&keywords=improve+your+chess+tactics, as well as Reinfeld's "1001" books.

Yeah right.

I suggest "Storming the Barricades" by Larry Christiansen, it is instructive and at the same time somehow inspirational since tha author also tells a bit about how he came to be a grandmaster.

Thanks Mvtjc