Perhaps you should try some spelling variations:
trinh vat » trinh van, trinh luat, sinh vat
ban trinh » ban tinh, dan trinh, van trinh
hieu van » hieu va, thien van, lieu va
dang xay » dang van, van xay
chat cua » nhat cua, chat va, chat huu
tu sach » thu sach, su sach, te sach
vat cua » mat cua, bat cua, dat cua
cua tre » cua te, cuu tre, cua triet
sach ty » sach y, sach tu, sach thu
hieu ve » hieu va
dong ha » dong hoa, dong va, dong hoc

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 ((dang xay) or (dong ha)) hoi. ((hieu ve) or (hieu van)) chat cua ban trinh vat cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty ((dang xay) OR (dong ha)) hoi. ((hieu ve) OR (hieu van)) chat cua ban trinh vat cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ty ((dang xay) or (dong ha)) hoi. ((hieu ve) or (hieu van)) chat cua ban trinh vat cua tre*.