Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
hieu van » hieu va, thien van, lieu va
cam thuc » am thuc, nam thuc, cam thu
thuc dan » thuc hanh, hoc dan, thuc vat
dan hanh » dang hanh, dan khanh, dan thanh
hanh dai » hanh tai, hanh dao, vanh dai
cua viet » ca viet, hoa viet, cua vat
tu sach » thu sach, su sach, te sach
nang ma » tang ma, sang ma, nang cao
van cam » van nam, van lam, van cau
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: ((tu sach) or (hoc sach)) ky nang ma hoi. hieu van cam thuc dan hanh dai cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (hoc sach)) ky nang ma hoi. hieu van cam thuc dan hanh dai cua viet.
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (hoc sach)) ky nang ma hoi. hieu van cam thuc dan hanh dai cua viet*.