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

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