Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
mai khoi » mai khoa, tai khoa, cac khoi
hanh tai » thanh tai, hang tai, han tai
hieu van » hieu va, thien van, lieu va
mai hoi » dai hoi, lai hoi, mai doi
sach ky » sac ky, sach y, sach ty
van lam » van nam
lam duc » lam duoc, pham duc, nam duoc
ky tang » ky nang, ky dang, kho tang
hanh va » hang va, hanh vi
tu sach » thu sach, su sach, te sach

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