Perhaps you should try some spelling variations:
thuat sach » thuat lanh, thuat san
hanh tai » thanh tai, hang tai, hinh tai
sach tu » sach thu, cach tu, sach ty
han tai » hang tai, nhan tai, van tai
kham ly » khao ly, khanh ly
vu kham » vu khanh
hieu vu » hieu va, hieu ve, hieu su
nang ma » tang ma, sang ma, mang may
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: thuat sach tu ((nang ma) or (nang cao)) hoi. hieu vu kham ly va ((hanh tai) OR (han tai)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thuat sach tu ((nang ma) OR (nang cao)) hoi. hieu vu kham ly va ((hanh tai) OR (han tai)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thuat sach tu ((nang ma) or (nang cao)) hoi. hieu vu kham ly va ((hanh tai) OR (han tai)) cua tre".
• Adding a wildcard symbol may retrieve word variants: thuat sach tu ((nang ma) or (nang cao)) hoi. hieu vu kham ly va ((hanh tai) OR (han tai)) cua tre*.