Perhaps you should try some spelling variations:
nam thuc » nam thuoc, am thuc, nam thu
dau tren » dau tien, dat tren, dau tieng
tu sach » thu sach, te sach, tu cach
su sach » so sach, vu sach
cao hoi » cau hoi, co hoi, cao hoc
hieu ve » hieu va, hieu van
vat dau » bat dau, va dau, van dau
ve nam » he nam, va nam, le nam
dau ca » dau cay, dau cua, dan ca
ca dau » ca dao, ca dan, 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: ((((thu hoach) or (tu sach))) or (su sach)) ky nang cao hoi. hieu ve nam thuc vat dau ca dau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((((thu hoach) OR (tu sach))) OR (su sach)) ky nang cao hoi. hieu ve nam thuc vat dau ca dau tren.
• Adding a wildcard symbol may retrieve word variants: ((((thu hoach) or (tu sach))) or (su sach)) ky nang cao hoi. hieu ve nam thuc vat dau ca dau tren*.