In NUS Central Library, the Reference section is on level 5 and it is a quiet area. To locate design and art-related books, use the Library of Congress Subject Headings
NK = Applied arts; decorative arts and ornaments (including design)
NX = A broad classification that covers Arts (broadly defined) including art media (eg. site-specific art) and movements (eg. surrealism).
TS171 = Production matters relating to design.