Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
cua tre » cua te, cuu tre, cua triet
va hanh » van hanh, va thanh, va danh
bac bao » bac bo, tac bao, bac cao
sach ky » sach y, sach ty, sach kem
hieu ve » hieu va, hieu van
sac ky » cac ky, sai ky
bao va » bao ve, tao va, ban va
ve bac » ve bao, ve cac, ve ban
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: su ((sach ky) or (sac ky)) nang x hoi. hieu ve bac bao va hanh vi ((cua tre) or (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ky) OR (sac ky)) nang x hoi. hieu ve bac bao va hanh vi ((cua tre) OR (cau tren)).
• Adding a wildcard symbol may retrieve word variants: su ((sach ky) or (sac ky)) nang x hoi. hieu ve bac bao va hanh vi ((cua tre) or (cau tren))*.