Perhaps you should try some spelling variations:
luat thuc » luat thue, luat tuc, luan thuc
cau tren » cu tren, dau tren, ca tren
tinh doi » trinh doc, trinh do, tinh hoc
hieu cua » dieu cua, bieu cua, hieu ca
sang ma » tang ma, sang tao, mang may
sach ky » sac ky, sach y, sach ty
thuc va » thuc vat, thuc dan, thuc day
va tinh » may tinh
nang ma » tang ma, nang cao, mang may
doi cau » doi dau, di cau, doi ca
te sach » toc sach

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sach ky ((nang ma) or (sang ma)) hoi. ((hieu cua) OR (hieu qua)) luat thuc va tinh doi cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ky ((nang ma) OR (sang ma)) hoi. ((hieu cua) OR (hieu qua)) luat thuc va tinh doi cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ky ((nang ma) or (sang ma)) hoi. ((hieu cua) OR (hieu qua)) luat thuc va tinh doi cau tren".
• Adding a wildcard symbol may retrieve word variants: te sach ky ((nang ma) or (sang ma)) hoi. ((hieu cua) OR (hieu qua)) luat thuc va tinh doi cau tren*.