Perhaps you should try some spelling variations:
vat thanh » dat thanh, gat thanh, tat thanh
nam thuc » nam thuoc, am thuc, nam thu
van hanh » van thanh, ban hanh, van anh
su sach » so sach, vu sach
sach ly » sach y, sach lo, sach ty
ly nang » ky nang, ly hang, ly vang
qua nam » quan nam, cua nam, quang nam
cua tre » cua te, cuu tre, cua triet
di cua » dai cua, doi cua, de cua
x hoi » xa hoi, o hoi, x ho

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 ly nang x hoi. hieu qua nam thuc ((((vat thanh) or (van hanh))) or (gia thanh)) di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ly nang x hoi. hieu qua nam thuc ((((vat thanh) OR (van hanh))) OR (gia thanh)) di cua tre.
• Adding a wildcard symbol may retrieve word variants: su sach ly nang x hoi. hieu qua nam thuc ((((vat thanh) or (van hanh))) or (gia thanh)) di cua tre*.