Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
tang mai » tang ma, tang tai, lang mai
hanh tai » thanh tai, hang tai, han tai
hieu van » hieu va, thien van, lieu va
mai hoi » mai khoi, dai hoi, lai hoi
sach ky » sach y, sach ty, sach kem
van lam » van nam
lam duc » lam duoc, pham duc, nam duoc
hanh va » hang va, hanh vi
sac ky » cac ky, sai ky

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) OR (sac ky)) tang mai hoi. 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) OR (sac ky)) tang mai hoi. 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) OR (sac ky)) tang mai hoi. hieu van lam duc va ((hanh tai) or (hanh va)) cau tren".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) OR (sac ky)) tang mai hoi. hieu van lam duc va ((hanh tai) or (hanh va)) cau tren*.