Perhaps you should try some spelling variations:
vat hanh » vat thanh, van hanh, va hanh
thi hang » thi hanh, thi nang, thi hong
hieu van » hieu va, thien van, lieu va
tu sach » thu sach, su sach, te sach
hanh te » hanh tu, hanh ve, hanh de
cuu tac » cuu dac, cuu cac, cuu xac
ty hang » ly hang, ty xang, thu hang
te cua » tue cua, le cua, de cua
cua tu » cua tuc, cua su, cua cu

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 ((ty hang) or (thi hang)) xa hoi. hieu van ((cuu thuc) or (cuu tac)) vat hanh te cua tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ty hang) OR (thi hang)) xa hoi. hieu van ((cuu thuc) OR (cuu tac)) vat hanh te cua tu.
• Adding a wildcard symbol may retrieve word variants: tu sach ((ty hang) or (thi hang)) xa hoi. hieu van ((cuu thuc) or (cuu tac)) vat hanh te cua tu*.