Perhaps you should try some spelling variations:
dang xay » dang van, van xay
thuc dan » thuc hanh, hoc dan, thuc vat
tu sach » thu sach, su sach, te sach
thuc va » thuc vat, thuc day
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
lang ha » long ha
cua tre » cua te, cuu tre, cua triet
ve cac » va cac, vien cac
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: tu sach ky ((dang xay) or (lang ha)) hoi. hieu ve cac ((thuc va) OR (thuc dan)) hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((dang xay) OR (lang ha)) hoi. hieu ve cac ((thuc va) OR (thuc dan)) hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((dang xay) or (lang ha)) hoi. hieu ve cac ((thuc va) OR (thuc dan)) hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((dang xay) or (lang ha)) hoi. hieu ve cac ((thuc va) OR (thuc dan)) hanh vi cua tre*.