Heading 5901 covers fabrics coated with gum, starch, or similar substances specifically for use as outer covers of books, registers, or similar articles. Heading 5903 covers fabrics impregnated or coated with plastics (PVC, polyurethane, or other). The coating substance and the intended end use together determine which heading applies.

Yes. Prepared painting canvas—fabric primed or sized for use as an artist's painting surface—classifies under 5901 regardless of whether the base is cotton, linen, or another fiber. The preparation for painting use is the controlling factor, not the underlying fiber composition.