Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
cam thuc » am thuc, nam thuc, cam thu
hieu van » hieu va, thien van, lieu va
mai khoi » mai khoa, tai khoa, cac khoi
thu sach » tu sach, thuat sach, thuoc sach
cua viet » ca viet, hoa viet, cua vat
van cam » van nam, van lam, van cau
thuc va » thuc vat, thuc dan, thuc day
va hanh » van hanh, va thanh, va danh
hanh de » hanh ve, hanh kem
ma hoi » mai hoi, xa hoi, ma hoa
de cua » le cua, te cua, dieu cua

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

• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (thu sach)) ky nang ((ma hoi) OR (mai khoi)). hieu van cam thuc va hanh de cua viet~.
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (thu sach)) ky nang ((ma hoi) or (mai khoi)). hieu van cam thuc va hanh de cua viet*.