Perhaps you should try some spelling variations:
tan hanh » tan thanh, tang hanh, toan hanh
hieu van » hieu va, thien van, lieu va
sach tu » sach thu, cach tu, sach ty
cua tre » cua te, cua triet, dua tren
nam duc » nam duoc, pham duc, nam thuc
su sach » so sach, vu sach
nang ma » tang ma, sang ma, nang cao
lang ha » long ha
cuu tre » cau tren, cau treo

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 tu ((lang ha) or (nang ma)) hoi. hieu van nam duc tan hanh vi ((cua tre) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach tu ((lang ha) OR (nang ma)) hoi. hieu van nam duc tan hanh vi ((cua tre) OR (cuu tre)).
• Adding a wildcard symbol may retrieve word variants: su sach tu ((lang ha) or (nang ma)) hoi. hieu van nam duc tan hanh vi ((cua tre) or (cuu tre))*.