Perhaps you should try some spelling variations:
dau tren » dau tien, dat tren, dau tieng
nam thuc » nam thuoc, am thuc, nam thu
hieu van » hieu va, thien van, lieu va
du tren » dua tren, duc tren, tu tren
hang vi » hang va, hanh vi, hang di
va hang » van hang, va nang, va lang
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
nam luc » nang luc, nhan luc, nam duoc
lang ha » long ha
ky lang » ky nang, ky dang, ky tang
ha hoi » hoa hoi, ha noi, xa hoi

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

• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky lang ha hoi. hieu van ((nam luc) OR (nam thuc)) va hang vi ((du tren) OR (dau tren))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky lang ha hoi. hieu van ((nam luc) or (nam thuc)) va hang vi ((du tren) OR (dau tren))~".
• Adding a wildcard symbol may retrieve word variants: tu sach ky lang ha hoi. hieu van ((nam luc) or (nam thuc)) va hang vi ((du tren) OR (dau tren))*.