Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
sach doi » sach hoi, sach moi, sach dao
vat hanh » vat thanh, van hanh, va hanh
nam thuc » nam thuoc, am thuc, nam thu
hanh vu » hanh vi, hanh va, hanh tu
hieu va » lieu va, hieu qua
thi van » thi lan, thi hanh, thi nang
tang ma » mang may, tang van
nang ma » sang ma, nang cao, mang may
va viet » hoa viet, san viet, mai viet
vu va » vu van, tu va, su va

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach doi ((nang ma) or (tang ma)) hoi. ((thi van) or (hieu va)) nam thuc vat hanh vu va viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach doi ((nang ma) OR (tang ma)) hoi. ((thi van) OR (hieu va)) nam thuc vat hanh vu va viet.
• Adding a wildcard symbol may retrieve word variants: thu sach doi ((nang ma) or (tang ma)) hoi. ((thi van) or (hieu va)) nam thuc vat hanh vu va viet*.