Hector,
not sure how much $$ you are willing to invest in your 'research library', but htere is an OOP hardcover w/ illustrations by Rikyu Watanabe for the B-17. go to amazon.com, put his name in the search box, pick 'books' as the category.
there will be a list of 20 or so books he has illustrated. used copies of "B-17: Flying Fortress" are available for $25 and up. i have a copy ordered, but have not seen it yet. i HAVE seen a good deal of his other work, and am pretty sure i will not be disappointed.
you may also see copies of other planes of interest on the list. a few years back i picked up a used copy of the "Great Book of WWII Airplanes" as a gift for my buddy for around $40. unfortunately, the book now commands a much higher price. it contains 10 or 12 of his other works under one cover. most of the individual books are available at a much more reasonable price.
good luck,
ed.