Perhaps you should try some spelling variations:
vat xanh » vat thanh, sat anh, dat anh
xanh doi » xanh di, thanh doi, tinh doi
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
van bac » van ban, van bao, dan bac
van hac » van hoc, van ha, van hai
doi cua » dai cua, hoi cua
cua tre » cua te, cuu tre, cua triet
ma hoi » mai hoi, ma hoa, me hoi

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 ky nang ((ma hoi) OR (xa hoi)). hieu ((van bac) or (van hac)) thuc vat xanh doi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((ma hoi) OR (xa hoi)). hieu ((van bac) OR (van hac)) thuc vat xanh doi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ((ma hoi) OR (xa hoi)). hieu ((van bac) or (van hac)) thuc vat xanh doi cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((ma hoi) OR (xa hoi)). hieu ((van bac) or (van hac)) thuc vat xanh doi cua tre*.