Perhaps you should try some spelling variations:
vat thanh » dat thanh, gat thanh, tat thanh
vat hanh » van hanh, va hanh, nhat hanh
nam thuc » nam thuoc, am thuc, nam thu
tu sach » thu sach, te sach, tu cach
hieu ve » hieu va, hieu van
cua tre » cua te, cuu tre, cua triet
tang ha » lang ha, tang ma, trung ha
ky tang » ky nang, ky dang, kho tang
su sach » so sach, vu sach
de cua » le cua, te cua, dieu cua
ve nam » he nam, va nam, le nam

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 (su sach)) ky tang ha noi. hieu ve nam thuc ((vat hanh) OR (vat thanh)) de cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (su sach)) ky tang ha noi. hieu ve nam thuc ((vat hanh) OR (vat thanh)) de cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (su sach)) ky tang ha noi. hieu ve nam thuc ((vat hanh) OR (vat thanh)) de cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (su sach)) ky tang ha noi. hieu ve nam thuc ((vat hanh) OR (vat thanh)) de cua tre*.