Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
hanh vai » hanh vi, hanh va, hanh tai
thuc dan » thuc hanh, hoc dan, thuc vat
cua viet » ca viet, hoa viet, cua vat
lang van » dang van, tang van, hoang van
sach ty » sach y, sach tu, sach thu
thuc va » thuc vat, thuc day
lang xa » lang ha, dang xay
vai cua » dai cua, hai cua, lai cua
hieu vi » hieu voi, hieu va, hieu ve

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc sach ty ((lang xa) OR (lang van)) hoi. hieu vi pham ((thuc va) or (thuc dan)) hanh vai cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach ty ((lang xa) OR (lang van)) hoi. hieu vi pham ((thuc va) OR (thuc dan)) hanh vai cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach ty ((lang xa) OR (lang van)) hoi. hieu vi pham ((thuc va) or (thuc dan)) hanh vai cua viet".
• Adding a wildcard symbol may retrieve word variants: doc sach ty ((lang xa) OR (lang van)) hoi. hieu vi pham ((thuc va) or (thuc dan)) hanh vai cua viet*.