Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
va trinh » van trinh, va tinh, lap trinh
trinh ve » trinh he, trinh va, trinh vi
tu sach » thu sach, su sach, tu cach
te sach » toc sach
xang xa » lang xa, mang xa, ang xa
van cac » van hac, van cau, van bac
cua tu » cua tuc, cua cu, cua te
cua su » qua su

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