Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu cua » hieu qua, bieu cua, hieu ca
luat tuc » luat thue
dieu cua » dieu tra
cau treo » cau theo, cau tren, cau triet
sach ky » sac ky, sach y, sach ty
sang ma » tang ma, nang ma, sang tao
ky sang » ky nang, ky dang, ky tang
hoc cau » hoc cao, hoc cac, hoc can
ma hoi » mai hoi, xa hoi, ma hoa

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