Perhaps you should try some spelling variations:
cac trung » cac truong, dac trung, bac trung
hieu van » hieu va, thien van, lieu va
trung va » truong va, trang va, trung ha
cua tre » cuu tre, cua triet, dua tren
va hanh » van hanh, va thanh, va danh
van cac » van hac, van cau, van bac
sach ky » sac ky, sach y, sach kem
nang xa » nang x, lang xa, nang ma
sach ty » sach y, sach tu, sach thu
cua te » cua tu

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: su ((sach ky) OR (sach ty)) nang xa hoi. hieu van cac trung va hanh vi ((cua tre) OR (cua te))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach ky) or (sach ty)) nang xa hoi. hieu van cac trung va hanh vi ((cua tre) OR (cua te))~".
• Adding a wildcard symbol may retrieve word variants: su ((sach ky) or (sach ty)) nang xa hoi. hieu van cac trung va hanh vi ((cua tre) OR (cua te))*.