Perhaps you should try some spelling variations:
sach thu » sach thue, sach thieu, sach tham
thu nang » thi nang, thu hang, thu bang
dua tren » dung tren
van hanh » van thanh, ban hanh, van anh
tu sach » thu sach, su sach, te sach
cham oc » cham soc, cham o, cham hoi
hieu va » lieu va, hieu qua
hieu vu » hieu ve, hieu su, dieu vu
nang xa » nang x, lang xa, nang ma
cuu tre » cua tre, cau tren, cau treo
oc van » hoc van, luoc van, quoc van

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 thu nang xa hoi. ((hieu vu) or (hieu va)) cham oc van hanh vi ((dua tren) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach thu nang xa hoi. ((hieu vu) OR (hieu va)) cham oc van hanh vi ((dua tren) OR (cuu tre)).
• Adding a wildcard symbol may retrieve word variants: tu sach thu nang xa hoi. ((hieu vu) or (hieu va)) cham oc van hanh vi ((dua tren) or (cuu tre))*.