Perhaps you should try some spelling variations:
dau tien » van tien
hanh tai » thanh tai, hang tai, han tai
lang mai » lang dai, lang hai, lang man
hieu van » hieu va, thien van, lieu va
van cham » van chat, van tham, va cham
cham luc » cham soc, nhan luc, cham cuu
cu tren » tu tren, dua tren
hanh va » hang va, hanh vi
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
mai hoi » mai khoi, dai hoi, lai hoi
ky lang » ky nang, ky dang, ky tang
luc va » duc va, tuc va, loc va

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 lang mai hoi. hieu van cham luc va ((hanh tai) or (hanh va)) ((cu tren) or (dau tien))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky lang mai hoi. hieu van cham luc va ((hanh tai) OR (hanh va)) ((cu tren) OR (dau tien)).
• Adding a wildcard symbol may retrieve word variants: tu sach ky lang mai hoi. hieu van cham luc va ((hanh tai) or (hanh va)) ((cu tren) or (dau tien))*.