Perhaps you should try some spelling variations:
dang xay » dang van, van xay
hac nuoc » hoc nuoc, cac nuoc, phap nuoc
hieu van » hieu va, thien van, lieu va
tinh vi » trinh vi, tinh voi, tinh va
va tinh » may tinh
van hac » van hoc, van ha, van hai
tu sach » thu sach, te sach, tu cach
lang xa » lang ha, lang van
su sach » so sach, vu sach
vi cua » vai cua, di cua
cua tu » cua tuc, cua su, cua cu

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) or (su sach)) nay ((lang xa) OR (dang xay)) hoi. hieu van hac nuoc va tinh vi cua tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (su sach)) nay ((lang xa) OR (dang xay)) hoi. hieu van hac nuoc va tinh vi cua tu.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (su sach)) nay ((lang xa) OR (dang xay)) hoi. hieu van hac nuoc va tinh vi cua tu".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (su sach)) nay ((lang xa) OR (dang xay)) hoi. hieu van hac nuoc va tinh vi cua tu*.