Perhaps you should try some spelling variations:
thanh hai » thanh phan, thanh hoa, thanh san
thanh lap » thanh san, phan lap, thanh van
hieu van » hieu va, thien van, lieu va
tu sach » thu sach, su sach, te sach
van cac » van hac, van cau, van bac
cac duc » cac du, cao duc, cac dac
nang o » nang co, nang ho, nang ro
o hai » co hai, so hai, o lai

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 (thu hoach)) ky nang o hai. hieu van cac duc va ((thanh lap) OR (thanh hai)) cua vat~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu hoach)) ky nang o hai. hieu van cac duc va ((thanh lap) OR (thanh hai)) cua vat.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (thu hoach)) ky nang o hai. hieu van cac duc va ((thanh lap) OR (thanh hai)) cua vat".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (thu hoach)) ky nang o hai. hieu van cac duc va ((thanh lap) OR (thanh hai)) cua vat*.