Yoshiharu:
Greetings, I have seen your work in the critiques forum - you are making great strides.
My best advice when copying a master work is to get the best reference available to you. In my case, I found paintings that had large museum posters available of them. I used these as my base reference and found other images of the same painting in books, on the Internet, etc.
For The Storybook, I visited the LACMA museum in L.A. and viewed the original through binoculars - it was about 9 feet up on a wall behind some furniture on display. I gridded the painting off on a sheet of paper and took fairly copious notes for each square noting color, visible brush strokes, etc.
And finally, if you choose to copy any work, then make your copy at least 5% off of the size of the original. Never paint the original artist's signature. Sign your own name and put "After" and the original artists name. I do this in paint on the front, and on the back in pencil.
Good Luck!
