Perhaps you should try some spelling variations:
dau tren » dau tien, dat tren, dau tieng
luc ngan » luc nganh, luat ngan, vu ngan
thu nang » thi nang, thu hang, thu bang
hieu van » hieu va, thien van, lieu va
luc nhan » luc nhat, cu nhan, tue nhan
hang vi » hang va, hanh vi, hang di
van cam » van nam, van lam, van cau
tu sach » thu sach, su sach, te sach
vi dau » vi dai, va dau, bi dau
x hoi » xa hoi, o hoi, x ho

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((thu hoach) or (tu sach)) thu nang x hoi. hieu van cam ((luc ngan) or (luc nhan)) hang vi dau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((thu hoach) OR (tu sach)) thu nang x hoi. hieu van cam ((luc ngan) OR (luc nhan)) hang vi dau tren.
• Adding a wildcard symbol may retrieve word variants: ((thu hoach) or (tu sach)) thu nang x hoi. hieu van cam ((luc ngan) or (luc nhan)) hang vi dau tren*.