Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
hieu cua » hieu qua, dieu cua, bieu cua
sach thu » sach thue, sach thieu, sach tham
nang xa » nang x, lang xa, nang ma
sach ty » sach y, sach tu, xach tay
cua dai » cua dan, cua dang
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet
dai tu » dai thu, tai tu, mai 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)) nang xa hoi. hieu cua dai tu va hanh vi ((cua tre) or (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ty) OR (sach thu)) nang xa hoi. hieu cua dai tu va hanh vi ((cua tre) OR (cau tren)).
• Adding a wildcard symbol may retrieve word variants: su ((sach ty) or (sach thu)) nang xa hoi. hieu cua dai tu va hanh vi ((cua tre) or (cau tren))*.