Perhaps you should try some spelling variations:
hai huoc » thai hoc, hai muoi
vu sach » vu bach, su sach, vu khach
nang ma » tang ma, sang ma, nang cao
huoc va » thuoc va, hoc va, nuoc va
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cua triet, dua tren
cuu tre » cau tren, cau treo
va hai » van hai, va chai, va khai

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: vu sach y ((nang x) or (nang ma)) hoi. lieu va hai huoc va hanh vi ((cua tre) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach y ((nang x) OR (nang ma)) hoi. lieu va hai huoc va hanh vi ((cua tre) OR (cuu tre)).
• Adding a wildcard symbol may retrieve word variants: vu sach y ((nang x) or (nang ma)) hoi. lieu va hai huoc va hanh vi ((cua tre) or (cuu tre))*.