Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu cua » hieu qua, dieu cua, bieu cua
cua luat » quy luat
sach ky » sac ky, sach y, sach ty
thue va » thuc va, thuyet va, thuc vat
va tinh » may tinh
ky sang » ky nang, ky dang, ky tang
doi cuu » doi cuoc
doi cua » dai cua, hoi cua
ma hoi » mai hoi, ma hoa, me hoi

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 sang ((ma hoi) or (xa hoi)). hieu cua luat thue va tinh ((doi cuu) OR (doi cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky sang ((ma hoi) OR (xa hoi)). hieu cua luat thue va tinh ((doi cuu) OR (doi cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky sang ((ma hoi) or (xa hoi)). hieu cua luat thue va tinh ((doi cuu) OR (doi cua)) tre".
• Adding a wildcard symbol may retrieve word variants: toc sach ky sang ((ma hoi) or (xa hoi)). hieu cua luat thue va tinh ((doi cuu) OR (doi cua)) tre*.