Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
dung sai » dung tai, dung va, dung dat
cua viet » ca viet, hoa viet, cua vat
ky lang » ky nang, ky dang, ky tang
lang xa » lang ha, dang xay, lang van
sach ky » sac ky, sach y, sach ty
va dung » van dung, va duong, vat dung
cua tu » cua tuc, cua su, cua cu
va cao » va cac, va co, va dao
va cam » va cham, va cac, va cai

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