Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
su sach » so sach, vu sach
sach ty » sach y, sach tu, sach thu
nang xa » lang xa, nang ma, mang xa
hieu ve » hieu va, hieu van
ve pham » vi pham, v pham, ve phan
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.

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ty ((nang xa) OR (nang x)) hoi. hieu ve pham duc va hanh vi ((cua tre) or (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty ((nang xa) OR (nang x)) hoi. hieu ve 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 ((nang xa) OR (nang x)) hoi. hieu ve pham duc va hanh vi ((cua tre) or (cau tren))".
• Adding a wildcard symbol may retrieve word variants: su sach ty ((nang xa) OR (nang x)) hoi. hieu ve pham duc va hanh vi ((cua tre) or (cau tren))*.