Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
toc sach » hoc sach, doc sach, nuoc sach
cua viet » ca viet, hoa viet, cua vat
ky lang » ky nang, ky dang, ky tang
lang xa » lang ha, dang xay, lang van
hieu ve » hieu va, hieu van
cac tuc » cac tu, cac tac, cac nuoc
cac toc » cac toi, cac nuoc, cac thoi
va dau » va dao
dau vi » dau ve, dau va, dat vi
vi cua » vai cua, di cua

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: ((toc sach) OR (thuoc sach)) ky lang xa hoi. hieu ve ((cac tuc) or (cac toc)) va dau vi cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (thuoc sach)) ky lang xa hoi. hieu ve ((cac tuc) OR (cac toc)) va dau vi cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) OR (thuoc sach)) ky lang xa hoi. hieu ve ((cac tuc) or (cac toc)) va dau vi cua viet".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) OR (thuoc sach)) ky lang xa hoi. hieu ve ((cac tuc) or (cac toc)) va dau vi cua viet*.