Perhaps you should try some spelling variations:
doc sach » hoc sach, nuoc sach, dac sac
thuc dan » thuc hanh, hoc dan, thuc vat
cua viet » ca viet, hoa viet, cua vat
toc sach » hoc sach, thuoc sach, nuoc sach
xang xa » lang xa, mang xa, ang xa
hieu ve » hieu va, hieu van
thuc va » thuc vat, thuc day
ve pham » vi pham, v pham, ve phan
vi cua » vai cua, di cua

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) or (toc sach)) ty xang xa hoi. hieu ve pham ((thuc va) or (thuc dan)) hanh vi cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((doc sach) OR (toc sach)) ty xang xa hoi. hieu ve pham ((thuc va) OR (thuc dan)) hanh vi cua viet.
• Adding a wildcard symbol may retrieve word variants: ((doc sach) or (toc sach)) ty xang xa hoi. hieu ve pham ((thuc va) or (thuc dan)) hanh vi cua viet*.