Perhaps you should try some spelling variations:
hanh tai » thanh tai, hang tai, han tai
hieu van » hieu va, thien van, lieu va
sach ty » sach y, sach tu, sach thu
nang ma » tang ma, sang ma, nang cao
sach ky » sac ky, sach y, sach kem
van cau » van dau, van hau, van chat
cau luc » cau truc, cau phuc
va hanh » van hanh, va thanh, va danh
cua tre » cuu tre, cua triet, dua tren
ma hoi » mai hoi, xa hoi, ma hoa
luc va » duc va, tuc va, loc va
cua te » cua tu

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

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