Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
thanh vi » hanh vi, thanh va, thanh ve
cua tre » cua te, cuu tre, cua triet
dua ban » dia ban, cua ban, qua ban
sach ty » sach y, sach tu, sach thu
so sach » so sanh, bo sach, co sach
duc ban » duc tan, duc van, duc man
va chat » van chat, va phat, cao chat
hieu va » lieu va, hieu qua
ty nang » ky nang, ty xang, ty hang
nang o » nang co, nang ho, nang ro
o hoi » co hoi, o hoc, o hai

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ty nang o hoi. hieu va chat ((duc ban) OR (dua ban)) thanh vi ((cua tre) or (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ty nang o hoi. hieu va chat ((duc ban) OR (dua ban)) thanh vi ((cua tre) OR (cau tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ty nang o hoi. hieu va chat ((duc ban) OR (dua ban)) thanh vi ((cua tre) or (cau tren))".
• Adding a wildcard symbol may retrieve word variants: so sach ty nang o hoi. hieu va chat ((duc ban) OR (dua ban)) thanh vi ((cua tre) or (cau tren))*.