Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
xach tay » canh tay
cach tay » canh tay, cach ta, cach tu
cau hoc » cau hoi, cau hoa, cao hoc
hoc van » hoc dan, hoc va, hoc vat
hieu ke » hieu kem, chieu ke, hieu ky
lang ha » long ha
ke cau » ket cau
di cua » doi cua, de cua, do cua

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

• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((cach tay) OR (xach tay)) lang ha noi. hieu ke cau hoc van hanh ((di cua) OR (dai cua)) te~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((cach tay) or (xach tay)) lang ha noi. hieu ke cau hoc van hanh ((di cua) OR (dai cua)) te~".
• Adding a wildcard symbol may retrieve word variants: tu ((cach tay) or (xach tay)) lang ha noi. hieu ke cau hoc van hanh ((di cua) OR (dai cua)) te*.