Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
ban hanh » ban hang
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
cua tre » cua te, cuu tre, cua triet
va tinh » may tinh
tu sach » thu sach, su sach, te sach
sach ty » sach y, sach tu, sach thu
qua cac » cua cac
lang xa » lang ha, dang xay, lang van
ty lang » tay lang, ty xang, ty hang

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ty lang xa hoi. hieu qua cac nuoc ((ban hanh) or (va tinh)) vi ((cua tre) or (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty lang xa hoi. hieu qua cac nuoc ((ban hanh) OR (va tinh)) vi ((cua tre) OR (cau tren)).
• Adding a wildcard symbol may retrieve word variants: tu sach ty lang xa hoi. hieu qua cac nuoc ((ban hanh) or (va tinh)) vi ((cua tre) or (cau tren))*.