Perhaps you should try some spelling variations:
thuc dan » thuc hanh, hoc dan, thuc vat
hieu van » hieu va, thien van, lieu va
cuu tre » cua tre, cau tren, cau treo
van cau » van dau, van hau, van chat
lang xa » lang ha, dang xay, lang van
sac ky » cac ky, sai ky
xac va » tac va, ac va, bac va
vi cuu » vi luu, vinh cuu

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

• Performing a fuzzy search may retrieve terms with similar spellings: so ((sac ky) or (sach y)) lang xa hoi. hieu van cau ((xac va) or (thuc dan)) hanh vi cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so ((sac ky) OR (sach y)) lang xa hoi. hieu van cau ((xac va) OR (thuc dan)) hanh vi cuu tre.
• Adding a wildcard symbol may retrieve word variants: so ((sac ky) or (sach y)) lang xa hoi. hieu van cau ((xac va) or (thuc dan)) hanh vi cuu tre*.