Perhaps you should try some spelling variations:
hieu cua » hieu qua, dieu cua, bieu cua
sach thu » sach thue, sach thieu, sach tham
cua tre » cua te, cuu tre, cua triet
va hanh » van hanh, va thanh, va danh
cua dam » cua dan, cua dai, cua tam
sach ty » sach y, sach tu, xach tay
lang xa » lang ha, dang xay, lang van
ca tren » cau tren, cu tren, la tren
dam tu » nam tu, cam tu, tam tu

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 ty) or (sach thu)) lang xa hoi. hieu cua dam tu va hanh vi ((cua tre) or (ca tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ty) OR (sach thu)) lang xa hoi. hieu cua dam tu va hanh vi ((cua tre) OR (ca tren)).
• Adding a wildcard symbol may retrieve word variants: su ((sach ty) or (sach thu)) lang xa hoi. hieu cua dam tu va hanh vi ((cua tre) or (ca tren))*.