Perhaps you should try some spelling variations:
lang van » dang van, tang van, hoang van
hieu cua » hieu qua, dieu cua, bieu cua
nam thuc » nam thuoc, am thuc, nam thu
vat dung » van dung, va dung, viet dung
dung dai » duong dai, dung tai, dung dat
sach ty » sach tu, sach thu, xach tay
cua nam » cua tam, cua ngan, cua nhan
cua tre » cua te, cuu tre, cua triet

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

• Performing a fuzzy search may retrieve terms with similar spellings: su ((sach ty) or (sach y)) ((lang van) or (nang x)) hoi. hieu cua nam thuc vat dung dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ty) OR (sach y)) ((lang van) OR (nang x)) hoi. hieu cua nam thuc vat dung dai cua tre.
• Adding a wildcard symbol may retrieve word variants: su ((sach ty) or (sach y)) ((lang van) or (nang x)) hoi. hieu cua nam thuc vat dung dai cua tre*.