Perhaps you should try some spelling variations:
thuat san » thuat toan, thuat song, thuat lanh
van hanh » van thanh, ban hanh, van anh
hieu van » hieu va, thien van, lieu va
tang ma » mang may, tang van
hac dat » tac dat, hoach dat, nhac dan
hoc dat » hoc dan, hoc dai, hoc phat
nang ma » sang ma, nang cao, mang may
san ky » sang ky, van ky, dan ky
vi cua » vai cua, di cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: thuat san ky ((nang ma) or (tang ma)) hoi. hieu van ((hac dat) OR (hoc dat)) van hanh vi cua vat~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thuat san ky ((nang ma) OR (tang ma)) hoi. hieu van ((hac dat) OR (hoc dat)) van hanh vi cua vat.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thuat san ky ((nang ma) or (tang ma)) hoi. hieu van ((hac dat) OR (hoc dat)) van hanh vi cua vat".
• Adding a wildcard symbol may retrieve word variants: thuat san ky ((nang ma) or (tang ma)) hoi. hieu van ((hac dat) OR (hoc dat)) van hanh vi cua vat*.