Perhaps you should try some spelling variations:
nam thuoc » nam thuc, nam thu, nha thuoc
hieu quan » lieu quan, thien quan, lien quan
manh hai » lanh hai, minh hai, thanh hai
thuoc ma » hoc ma, duoc ma
tu sach » thu sach, te sach, tu cach
hai cua » thai cua, dai cua, hoi cua
ma manh » mai manh, ha manh, van manh
cua tre » cua te, cuu tre, cua triet
cao hoi » cau hoi, co hoi, cao hoc
su sach » so sach, vu sach

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 nang cao hoi. ((hieu quan) or (hieu qua)) nam thuoc ma manh hai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (su sach)) ky nang cao hoi. ((hieu quan) OR (hieu qua)) nam thuoc ma manh hai cua tre.
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (su sach)) ky nang cao hoi. ((hieu quan) or (hieu qua)) nam thuoc ma manh hai cua tre*.