Perhaps you should try some spelling variations:
sach thu » sach thue, sach thieu, sach tham
hieu van » hieu va, thien van, lieu va
van pham » san pham, van phan, van phat
cau tren » cu tren, dau tren, ca tren
sach ty » sach y, sach tu, xach tay
nang xa » nang x, lang xa, nang ma
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet

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 ty) OR (sach thu)) nang xa hoi. hieu van pham duc va hanh vi ((cua tre) OR (cau tren))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach ty) OR (sach thu)) nang xa hoi. hieu van pham duc 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 van pham duc va hanh vi ((cua tre) or (cau tren))*.