Perhaps you should try some spelling variations:
lam duoc » nam duoc, luat duoc, lam thuoc
tang mai » tang ma, tang tai, lang mai
hanh tai » thanh tai, hang tai, han tai
hieu van » hieu va, thien van, lieu va
tu sach » thu sach, su sach, te sach
hanh va » hang va, hanh vi
cuu tre » cua tre, cau tren, cau treo
sach ky » sac ky, sach y, sach ty
lam duc » pham duc, nam duoc, lam dung
mai hoi » mai khoi, dai hoi, lai hoi
ky tang » ky nang, ky dang, kho tang

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

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