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