Perhaps you should try some spelling variations:
cac thuc » cach thuc, cac thu, can thuc
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
cao hoi » cau hoi, co hoi, cao hoc
hieu ve » hieu va, hieu van
thuc va » thuc vat, thuc dan, thuc day
la tren » loai tren, dua tren, dat tren
cu tren » tu tren, dua tren
ve cac » va cac, vien cac
va dan » ca dan, va dao, va dau

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky nang cao hoi. hieu ve cac thuc va dan ca ((la tren) or (cu tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang cao hoi. hieu ve cac thuc va dan ca ((la tren) OR (cu tren)).
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang cao hoi. hieu ve cac thuc va dan ca ((la tren) or (cu tren))*.