Perhaps you should try some spelling variations:
cai viet » mai viet, tai viet, ca viet
thuc day » thuc dan, thuc vat
hieu van » hieu va, thien van, lieu va
lang ha » long ha
sach ty » sach y, sach tu, sach thu
thuc va » thuc vat, thuc dan
lang xa » dang xay, lang van
tu sach » thu sach, su sach, te sach
va cai » va cac, va bai, va dai

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 sach ty ((lang xa) OR (lang ha)) hoi. hieu van nam ((thuc va) OR (thuc day)) tich va cai viet~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty ((lang xa) or (lang ha)) hoi. hieu van nam ((thuc va) OR (thuc day)) tich va cai viet~".
• Adding a wildcard symbol may retrieve word variants: tu sach ty ((lang xa) or (lang ha)) hoi. hieu van nam ((thuc va) OR (thuc day)) tich va cai viet*.