Perhaps you should try some spelling variations:
trinh ket » tinh ket, trinh ke, trinh kiem
va trinh » van trinh, va tinh, lap trinh
te sach » toc sach
sach ty » sach y, sach tu, sach thu
tang ma » tang van
hieu ve » hieu va, hieu van
cac duc » cac du, cao duc, cac dac
qua tre » cua tre, quan tren, quan tri

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sach ty ((tang ma) OR (mang may)) hoi. ((hieu ve) or (lieu va)) cac duc va trinh ket qua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ty ((tang ma) OR (mang may)) hoi. ((hieu ve) OR (lieu va)) cac duc va trinh ket qua tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ty ((tang ma) OR (mang may)) hoi. ((hieu ve) or (lieu va)) cac duc va trinh ket qua tre*".