Perhaps you should try some spelling variations:
thanh tai » thanh hai, thanh toan, doanh tai
hieu van » hieu va, thien van, lieu va
va thanh » gia thanh, ban thanh, va tinh
cua tre » cua te, cua triet, dua tren
nam duc » nam duoc, pham duc, nam thuc
nang ma » tang ma, sang ma, nang cao
sach ty » sach y, sach tu, sach thu
cuu tre » cau tren, cau treo
ma hoi » mai hoi, xa hoi, ma hoa
sai ky » sac ky

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu ((sai ky) or (sach ty)) nang ma hoi. hieu van nam duc va thanh tai ((cua tre) OR (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu ((sai ky) OR (sach ty)) nang ma hoi. hieu van nam duc va thanh tai ((cua tre) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu ((sai ky) or (sach ty)) nang ma hoi. hieu van nam duc va thanh tai ((cua tre) OR (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: thu ((sai ky) or (sach ty)) nang ma hoi. hieu van nam duc va thanh tai ((cua tre) OR (cuu tre))*.